I'm using Entity Framework version 1, and i'm trying to create a generic repository, but I can't find a way to get the Primary Key of each table. Has anyone solved this issue?
UPDATE: My target use for this would be for a generic method that looks like this:
TModel GetByPrimaryKey(Guid key)
{
}
In the end, I adapted #Marc's answer from here: C# Linq-SQL: An UpdateByID method for the Repository Pattern
The result is something like this:
public TModel GetByPrimaryKey(Guid key)
{
// get the row from the database using the meta-model
MetaType meta = _DB.Mapping.GetTable(typeof(TModel)).RowType;
if (meta.IdentityMembers.Count != 1) throw new InvalidOperationException("Composite identity not supported");
string idName = meta.IdentityMembers[0].Member.Name;
var param = Expression.Parameter(typeof(TModel), "row");
var lambda = Expression.Lambda<Func<TModel, bool>>(
Expression.Equal(
Expression.PropertyOrField(param, idName),
Expression.Constant(key, typeof(Guid))), param);
return _DB.GetTable<TModel>().FirstOrDefault(lambda);
}
...where _DB is a DataContext.
I hope this helps someone in the future.
You have to use some kind of reflection.
Try something like this:
private PropertyInfo GetPrimaryKeyInfo<T>()
{
PropertyInfo[] properties = typeof(T).GetProperties();
foreach (PropertyInfo pI in properties)
{
System.Object[] attributes = pI.GetCustomAttributes(true);
foreach (object attribute in attributes)
{
if (attribute is EdmScalarPropertyAttribute)
{
if ((attribute as EdmScalarPropertyAttribute).EntityKeyProperty == true)
return pI;
}
else if (attribute is ColumnAttribute)
{
if ((attribute as ColumnAttribute).IsPrimaryKey == true)
return pI;
}
}
}
return null;
}
Related
I am one of the many struggling to "upgrade" from ASP.NET to ASP.NET Core.
In the ASP.NET project, I made database calls from my DAL like so:
var result = context.Database.SqlQuery<Object_VM>("EXEC [sp_Object_GetByKey] #Key",
new SqlParameter("#Key", Key))
.FirstOrDefault();
return result;
My viewmodel has additional fields that my object does not, such as aggregates of related tables. It seems unnecessary and counter intuitive to include such fields in a database / table structure. My stored procedure calculates all those things and returns the fields as should be displayed, but not stored.
I see that ASP.NET Core has removed this functionality. I am trying to continue to use stored procedures and load view models (and thus not have the entity in the database). I see options like the following, but as a result I get "2", the number of rows being returned (or another mysterious result?).
using(context)
{
string cmd = "EXEC [sp_Object_getAll]";
var result = context.Database.ExecuteSQLCommand(cmd);
}
But that won't work because context.Database.ExecuteSQLCommand is only for altering the database, not "selecting".
I've also seen the following as a solution, but the code will not compile for me, as "set" is really set<TEntity>, and there isn't a database entity for this viewmodel.
var result = context.Set().FromSql("EXEC [sp_Object_getAll]");
Any assistance much appreciated.
Solution:
(per Tseng's advice)
On the GitHub Entity Framework Issues page, there is a discussion about this problem. One user recommends creating your own class to handle this sort of requests, and another adds an additional method that makes it run smoother. I changed the methods slights to accept slightly different params.
Here is my adaptation (very little difference), for others that are also looking for a solution:
Method in DAL
public JsonResult GetObjectByID(int ID)
{
SqlParameter[] parms = new SqlParameter[] { new SqlParameter("#ID", ID) };
var result = RDFacadeExtensions.GetModelFromQuery<Object_List_VM>(context, "EXEC [sp_Object_GetList] #ID", parms);
return new JsonResult(result.ToList(), setting);
}
Additional Class
public static class RDFacadeExtensions
{
public static RelationalDataReader ExecuteSqlQuery(
this DatabaseFacade databaseFacade,
string sql,
SqlParameter[] parameters)
{
var concurrencyDetector = databaseFacade.GetService<IConcurrencyDetector>();
using (concurrencyDetector.EnterCriticalSection())
{
var rawSqlCommand = databaseFacade
.GetService<IRawSqlCommandBuilder>()
.Build(sql, parameters);
return rawSqlCommand
.RelationalCommand
.ExecuteReader(
databaseFacade.GetService<IRelationalConnection>(),
parameterValues: rawSqlCommand.ParameterValues);
}
}
public static IEnumerable<T> GetModelFromQuery<T>(
DbContext context,
string sql,
SqlParameter[] parameters)
where T : new()
{
DatabaseFacade databaseFacade = new DatabaseFacade(context);
using (DbDataReader dr = databaseFacade.ExecuteSqlQuery(sql, parameters).DbDataReader)
{
List<T> lst = new List<T>();
PropertyInfo[] props = typeof(T).GetProperties();
while (dr.Read())
{
T t = new T();
IEnumerable<string> actualNames = dr.GetColumnSchema().Select(o => o.ColumnName);
for (int i = 0; i < props.Length; ++i)
{
PropertyInfo pi = props[i];
if (!pi.CanWrite) continue;
System.ComponentModel.DataAnnotations.Schema.ColumnAttribute ca = pi.GetCustomAttribute(typeof(System.ComponentModel.DataAnnotations.Schema.ColumnAttribute)) as System.ComponentModel.DataAnnotations.Schema.ColumnAttribute;
string name = ca?.Name ?? pi.Name;
if (pi == null) continue;
if (!actualNames.Contains(name)) { continue; }
object value = dr[name];
Type pt = pi.DeclaringType;
bool nullable = pt.GetTypeInfo().IsGenericType && pt.GetGenericTypeDefinition() == typeof(Nullable<>);
if (value == DBNull.Value) { value = null; }
if (value == null && pt.GetTypeInfo().IsValueType && !nullable)
{ value = Activator.CreateInstance(pt); }
pi.SetValue(t, value);
}//for i
lst.Add(t);
}//while
return lst;
}//using dr
}
I have this method in my SurveyController class:
public ActionResult AddProperties(int id, int[] propertyids, int page = 1)
{
var survey = _uow.SurveyRepository.Find(id);
if (propertyids == null)
return GetPropertiesTable(survey, page);
var repo = _uow.PropertySurveyRepository;
propertyids.Select(propertyid => new PropertySurvey
{
//Setting the Property rather than the PropertyID
//prevents the error occurring later
//Property = _uow.PropertyRepository.Find(propertyid),
PropertyID = propertyid,
SurveyID = id
})
.ForEach(x => repo.InsertOrUpdate(x));
_uow.Save();
return GetPropertiesTable(survey, page);
}
The GetPropertiesTable redisplays Properties but PropertySurvey.Property is marked virtual and I have created the entity using the new operator, so a proxy to support lazy loading was never created and it is null when I access it. When we have access direct to the DbContext we can use the Create method to explicitly create the proxy. But I have a unit of work and repository pattern here. I guess I could expose the context.Create method via a repository.Create method and then I need to remember to use that instead of the new operator when I add an entity . But wouldn't it be better to encapsulate the problem in my InsertOrUpdate method? Is there some way to detect that the entity being added is not a proxy when it should be and substitute a proxy? This is my InsertOrUpdate method in my base repository class:
protected virtual void InsertOrUpdate(T e, int id)
{
if (id == default(int))
{
// New entity
context.Set<T>().Add(e);
}
else
{
// Existing entity
context.Entry(e).State = EntityState.Modified;
}
}
Based on the answer supplied by qujck. Here is how you can do it without having to employ automapper:
Edited to always check for proxy - not just during insert - as suggested in comments
Edited again to use a different way of checking whether a proxy was passed in to the method. The reason for changing the technique is that I ran into a problem when I introduced an entity that inherited from another. In that case an inherited entity can fail the entity.e.GetType().Equals(instance.GetType() check even if it is a proxy. I got the new technique from this answer
public virtual T InsertOrUpdate(T e)
{
DbSet<T> dbSet = Context.Set<T>();
DbEntityEntry<T> entry;
if (e.GetType().BaseType != null
&& e.GetType().Namespace == "System.Data.Entity.DynamicProxies")
{
//The entity being added is already a proxy type that supports lazy
//loading - just get the context entry
entry = Context.Entry(e);
}
else
{
//The entity being added has been created using the "new" operator.
//Generate a proxy type to support lazy loading and attach it
T instance = dbSet.Create();
instance.ID = e.ID;
entry = Context.Entry(instance);
dbSet.Attach(instance);
//and set it's values to those of the entity
entry.CurrentValues.SetValues(e);
e = instance;
}
entry.State = e.ID == default(int) ?
EntityState.Added :
EntityState.Modified;
return e;
}
public abstract class ModelBase
{
public int ID { get; set; }
}
I agree with you that this should be handled in one place and the best place to catch all looks to be your repository. You can compare the type of T with an instance created by the context and use something like Automapper to quickly transfer all of the values if the types do not match.
private bool mapCreated = false;
protected virtual void InsertOrUpdate(T e, int id)
{
T instance = context.Set<T>().Create();
if (e.GetType().Equals(instance.GetType()))
instance = e;
else
{
//this bit should really be managed somewhere else
if (!mapCreated)
{
Mapper.CreateMap(e.GetType(), instance.GetType());
mapCreated = true;
}
instance = Mapper.Map(e, instance);
}
if (id == default(int))
context.Set<T>().Add(instance);
else
context.Entry(instance).State = EntityState.Modified;
}
I'm trying to implement a caching scheme for my EF Repository similar to the one blogged here. As the author and commenters have reported the limitation is that the key generation method cannot produce cache keys that vary with a given query's parameters. Here is the cache key generation method:
private static string GetKey<T>(IQueryable<T> query)
{
string key = string.Concat(query.ToString(), "\n\r",
typeof(T).AssemblyQualifiedName);
return key;
}
So the following queries will yield the same cache key:
var isActive = true;
var query = context.Products
.OrderBy(one => one.ProductNumber)
.Where(one => one.IsActive == isActive).AsCacheable();
and
var isActive = false;
var query = context.Products
.OrderBy(one => one.ProductNumber)
.Where(one => one.IsActive == isActive).AsCacheable();
Notice that the only difference is that isActive = true in the first query and isActive = false in the second.
Any suggestions/insight to efficiently generating cache keys which vary by IQueryable parameters would be truly appreciated.
Kudos to Sergey Barskiy for sharing the EF CodeFirst caching scheme.
Update
I took the approach of traversing the IQueryable's expression tree myself with the goal of resolving the values of the parameters used in the query. With maxlego's suggestion, I extended the System.Linq.Expressions.ExpressionVisitor class to visit the expression nodes that we're interested in - in this case, the MemberExpression. The updated GetKey method looks something like this:
public static string GetKey<T>(IQueryable<T> query)
{
var keyBuilder = new StringBuilder(query.ToString());
var queryParamVisitor = new QueryParameterVisitor(keyBuilder);
queryParamVisitor.GetQueryParameters(query.Expression);
keyBuilder.Append("\n\r");
keyBuilder.Append(typeof (T).AssemblyQualifiedName);
return keyBuilder.ToString();
}
And the QueryParameterVisitor class, which was inspired by the answers of Bryan Watts and Marc Gravell to this question, looks like this:
/// <summary>
/// <see cref="ExpressionVisitor"/> subclass which encapsulates logic to
/// traverse an expression tree and resolve all the query parameter values
/// </summary>
internal class QueryParameterVisitor : ExpressionVisitor
{
public QueryParameterVisitor(StringBuilder sb)
{
QueryParamBuilder = sb;
Visited = new Dictionary<int, bool>();
}
protected StringBuilder QueryParamBuilder { get; set; }
protected Dictionary<int, bool> Visited { get; set; }
public StringBuilder GetQueryParameters(Expression expression)
{
Visit(expression);
return QueryParamBuilder;
}
private static object GetMemberValue(MemberExpression memberExpression, Dictionary<int, bool> visited)
{
object value;
if (!TryGetMemberValue(memberExpression, out value, visited))
{
UnaryExpression objectMember = Expression.Convert(memberExpression, typeof (object));
Expression<Func<object>> getterLambda = Expression.Lambda<Func<object>>(objectMember);
Func<object> getter = null;
try
{
getter = getterLambda.Compile();
}
catch (InvalidOperationException)
{
}
if (getter != null) value = getter();
}
return value;
}
private static bool TryGetMemberValue(Expression expression, out object value, Dictionary<int, bool> visited)
{
if (expression == null)
{
// used for static fields, etc
value = null;
return true;
}
// Mark this node as visited (processed)
int expressionHash = expression.GetHashCode();
if (!visited.ContainsKey(expressionHash))
{
visited.Add(expressionHash, true);
}
// Get Member Value, recurse if necessary
switch (expression.NodeType)
{
case ExpressionType.Constant:
value = ((ConstantExpression) expression).Value;
return true;
case ExpressionType.MemberAccess:
var me = (MemberExpression) expression;
object target;
if (TryGetMemberValue(me.Expression, out target, visited))
{
// instance target
switch (me.Member.MemberType)
{
case MemberTypes.Field:
value = ((FieldInfo) me.Member).GetValue(target);
return true;
case MemberTypes.Property:
value = ((PropertyInfo) me.Member).GetValue(target, null);
return true;
}
}
break;
}
// Could not retrieve value
value = null;
return false;
}
protected override Expression VisitMember(MemberExpression node)
{
// Only process nodes that haven't been processed before, this could happen because our traversal
// is depth-first and will "visit" the nodes in the subtree before this method (VisitMember) does
if (!Visited.ContainsKey(node.GetHashCode()))
{
object value = GetMemberValue(node, Visited);
if (value != null)
{
QueryParamBuilder.Append("\n\r");
QueryParamBuilder.Append(value.ToString());
}
}
return base.VisitMember(node);
}
}
I'm still doing some performance profiling on the cache key generation and hoping that it isn't too expensive (I'll update the question with the results once I have them). I'll leave the question open, in case anyone has suggestions on how to optimize this process or has a recommendation for a more efficient method for generating cache keys with vary with the query parameters. Although this method produces the desired output, it is by no means optimal.
i suggest to use ExpressionVisitor
http://msdn.microsoft.com/en-us/library/bb882521(v=vs.90).aspx
Just for the record, "Caching the results of LINQ queries" works well with the EF and it's able to work with parameters correctly, so it can be considered as a good second level cache implementation for EF.
While the solution of the OP works quite well, I found that the performance of the solution is a little bit poor.
The duration of the key generation varied between 300ms and 1200ms for my queries.
However, I've found another solution that has quite better performance (<10ms).
public static string ToTraceString<T>(DbQuery<T> query)
{
var internalQueryField = query.GetType().GetFields(BindingFlags.NonPublic | BindingFlags.Instance).Where(f => f.Name.Equals("_internalQuery")).FirstOrDefault();
var internalQuery = internalQueryField.GetValue(query);
var objectQueryField = internalQuery.GetType().GetFields(BindingFlags.NonPublic | BindingFlags.Instance).Where(f => f.Name.Equals("_objectQuery")).FirstOrDefault();
var objectQuery = objectQueryField.GetValue(internalQuery) as ObjectQuery<T>;
return ToTraceStringWithParameters(objectQuery);
}
private static string ToTraceStringWithParameters<T>(ObjectQuery<T> query)
{
string traceString = query.ToTraceString() + "\n";
foreach (var parameter in query.Parameters)
{
traceString += parameter.Name + " [" + parameter.ParameterType.FullName + "] = " + parameter.Value + "\n";
}
return traceString;
}
Like several other people, I'm having problems serializing Entity Framework objects, so that I can send the data over AJAX in a JSON format.
I've got the following server-side method, which I'm attempting to call using AJAX through jQuery
[WebMethod]
public static IEnumerable<Message> GetAllMessages(int officerId)
{
SIBSv2Entities db = new SIBSv2Entities();
return (from m in db.MessageRecipients
where m.OfficerId == officerId
select m.Message).AsEnumerable<Message>();
}
Calling this via AJAX results in this error:
A circular reference was detected while serializing an object of type \u0027System.Data.Metadata.Edm.AssociationType
Which is because of the way the Entity Framework creates circular references to keep all the objects related and accessible server side.
I came across the following code from (http://hellowebapps.com/2010-09-26/producing-json-from-entity-framework-4-0-generated-classes/) which claims to get around this problem by capping the maximum depth for references. I've added the code below, because I had to tweak it slightly to get it work (All angled brackets are missing from the code on the website)
using System.Web.Script.Serialization;
using System.Collections.Generic;
using System.Collections;
using System.Linq;
using System;
public class EFObjectConverter : JavaScriptConverter
{
private int _currentDepth = 1;
private readonly int _maxDepth = 2;
private readonly List<int> _processedObjects = new List<int>();
private readonly Type[] _builtInTypes = new[]{
typeof(bool),
typeof(byte),
typeof(sbyte),
typeof(char),
typeof(decimal),
typeof(double),
typeof(float),
typeof(int),
typeof(uint),
typeof(long),
typeof(ulong),
typeof(short),
typeof(ushort),
typeof(string),
typeof(DateTime),
typeof(Guid)
};
public EFObjectConverter( int maxDepth = 2,
EFObjectConverter parent = null)
{
_maxDepth = maxDepth;
if (parent != null)
{
_currentDepth += parent._currentDepth;
}
}
public override object Deserialize( IDictionary<string,object> dictionary, Type type, JavaScriptSerializer serializer)
{
return null;
}
public override IDictionary<string,object> Serialize(object obj, JavaScriptSerializer serializer)
{
_processedObjects.Add(obj.GetHashCode());
Type type = obj.GetType();
var properties = from p in type.GetProperties()
where p.CanWrite &&
p.CanWrite &&
_builtInTypes.Contains(p.PropertyType)
select p;
var result = properties.ToDictionary(
property => property.Name,
property => (Object)(property.GetValue(obj, null)
== null
? ""
: property.GetValue(obj, null).ToString().Trim())
);
if (_maxDepth >= _currentDepth)
{
var complexProperties = from p in type.GetProperties()
where p.CanWrite &&
p.CanRead &&
!_builtInTypes.Contains(p.PropertyType) &&
!_processedObjects.Contains(p.GetValue(obj, null)
== null
? 0
: p.GetValue(obj, null).GetHashCode())
select p;
foreach (var property in complexProperties)
{
var js = new JavaScriptSerializer();
js.RegisterConverters(new List<JavaScriptConverter> { new EFObjectConverter(_maxDepth - _currentDepth, this) });
result.Add(property.Name, js.Serialize(property.GetValue(obj, null)));
}
}
return result;
}
public override IEnumerable<System.Type> SupportedTypes
{
get
{
return GetType().Assembly.GetTypes();
}
}
}
However even when using that code, in the following way:
var js = new System.Web.Script.Serialization.JavaScriptSerializer();
js.RegisterConverters(new List<System.Web.Script.Serialization.JavaScriptConverter> { new EFObjectConverter(2) });
return js.Serialize(messages);
I'm still seeing the A circular reference was detected... exception being thrown!
I solved these issues with the following classes:
public class EFJavaScriptSerializer : JavaScriptSerializer
{
public EFJavaScriptSerializer()
{
RegisterConverters(new List<JavaScriptConverter>{new EFJavaScriptConverter()});
}
}
and
public class EFJavaScriptConverter : JavaScriptConverter
{
private int _currentDepth = 1;
private readonly int _maxDepth = 1;
private readonly List<object> _processedObjects = new List<object>();
private readonly Type[] _builtInTypes = new[]
{
typeof(int?),
typeof(double?),
typeof(bool?),
typeof(bool),
typeof(byte),
typeof(sbyte),
typeof(char),
typeof(decimal),
typeof(double),
typeof(float),
typeof(int),
typeof(uint),
typeof(long),
typeof(ulong),
typeof(short),
typeof(ushort),
typeof(string),
typeof(DateTime),
typeof(DateTime?),
typeof(Guid)
};
public EFJavaScriptConverter() : this(1, null) { }
public EFJavaScriptConverter(int maxDepth = 1, EFJavaScriptConverter parent = null)
{
_maxDepth = maxDepth;
if (parent != null)
{
_currentDepth += parent._currentDepth;
}
}
public override object Deserialize(IDictionary<string, object> dictionary, Type type, JavaScriptSerializer serializer)
{
return null;
}
public override IDictionary<string, object> Serialize(object obj, JavaScriptSerializer serializer)
{
_processedObjects.Add(obj.GetHashCode());
var type = obj.GetType();
var properties = from p in type.GetProperties()
where p.CanRead && p.GetIndexParameters().Count() == 0 &&
_builtInTypes.Contains(p.PropertyType)
select p;
var result = properties.ToDictionary(
p => p.Name,
p => (Object)TryGetStringValue(p, obj));
if (_maxDepth >= _currentDepth)
{
var complexProperties = from p in type.GetProperties()
where p.CanRead &&
p.GetIndexParameters().Count() == 0 &&
!_builtInTypes.Contains(p.PropertyType) &&
p.Name != "RelationshipManager" &&
!AllreadyAdded(p, obj)
select p;
foreach (var property in complexProperties)
{
var complexValue = TryGetValue(property, obj);
if(complexValue != null)
{
var js = new EFJavaScriptConverter(_maxDepth - _currentDepth, this);
result.Add(property.Name, js.Serialize(complexValue, new EFJavaScriptSerializer()));
}
}
}
return result;
}
private bool AllreadyAdded(PropertyInfo p, object obj)
{
var val = TryGetValue(p, obj);
return _processedObjects.Contains(val == null ? 0 : val.GetHashCode());
}
private static object TryGetValue(PropertyInfo p, object obj)
{
var parameters = p.GetIndexParameters();
if (parameters.Length == 0)
{
return p.GetValue(obj, null);
}
else
{
//cant serialize these
return null;
}
}
private static object TryGetStringValue(PropertyInfo p, object obj)
{
if (p.GetIndexParameters().Length == 0)
{
var val = p.GetValue(obj, null);
return val;
}
else
{
return string.Empty;
}
}
public override IEnumerable<Type> SupportedTypes
{
get
{
var types = new List<Type>();
//ef types
types.AddRange(Assembly.GetAssembly(typeof(DbContext)).GetTypes());
//model types
types.AddRange(Assembly.GetAssembly(typeof(BaseViewModel)).GetTypes());
return types;
}
}
}
You can now safely make a call like new EFJavaScriptSerializer().Serialize(obj)
Update : since version Telerik v1.3+ you can now override the GridActionAttribute.CreateActionResult method and hence you can easily integrate this Serializer into specific controller methods by applying your custom [GridAction] attribute:
[Grid]
public ActionResult _GetOrders(int id)
{
return new GridModel(Service.GetOrders(id));
}
and
public class GridAttribute : GridActionAttribute, IActionFilter
{
/// <summary>
/// Determines the depth that the serializer will traverse
/// </summary>
public int SerializationDepth { get; set; }
/// <summary>
/// Initializes a new instance of the <see cref="GridActionAttribute"/> class.
/// </summary>
public GridAttribute()
: base()
{
ActionParameterName = "command";
SerializationDepth = 1;
}
protected override ActionResult CreateActionResult(object model)
{
return new EFJsonResult
{
Data = model,
JsonRequestBehavior = JsonRequestBehavior.AllowGet,
MaxSerializationDepth = SerializationDepth
};
}
}
and finally..
public class EFJsonResult : JsonResult
{
const string JsonRequest_GetNotAllowed = "This request has been blocked because sensitive information could be disclosed to third party web sites when this is used in a GET request. To allow GET requests, set JsonRequestBehavior to AllowGet.";
public EFJsonResult()
{
MaxJsonLength = 1024000000;
RecursionLimit = 10;
MaxSerializationDepth = 1;
}
public int MaxJsonLength { get; set; }
public int RecursionLimit { get; set; }
public int MaxSerializationDepth { get; set; }
public override void ExecuteResult(ControllerContext context)
{
if (context == null)
{
throw new ArgumentNullException("context");
}
if (JsonRequestBehavior == JsonRequestBehavior.DenyGet &&
String.Equals(context.HttpContext.Request.HttpMethod, "GET", StringComparison.OrdinalIgnoreCase))
{
throw new InvalidOperationException(JsonRequest_GetNotAllowed);
}
var response = context.HttpContext.Response;
if (!String.IsNullOrEmpty(ContentType))
{
response.ContentType = ContentType;
}
else
{
response.ContentType = "application/json";
}
if (ContentEncoding != null)
{
response.ContentEncoding = ContentEncoding;
}
if (Data != null)
{
var serializer = new JavaScriptSerializer
{
MaxJsonLength = MaxJsonLength,
RecursionLimit = RecursionLimit
};
serializer.RegisterConverters(new List<JavaScriptConverter> { new EFJsonConverter(MaxSerializationDepth) });
response.Write(serializer.Serialize(Data));
}
}
You can also detach the object from the context and it will remove the navigation properties so that it can be serialized. For my data repository classes that are used with Json i use something like this.
public DataModel.Page GetPage(Guid idPage, bool detach = false)
{
var results = from p in DataContext.Pages
where p.idPage == idPage
select p;
if (results.Count() == 0)
return null;
else
{
var result = results.First();
if (detach)
DataContext.Detach(result);
return result;
}
}
By default the returned object will have all of the complex/navigation properties, but by setting detach = true it will remove those properties and return the base object only. For a list of objects the implementation looks like this
public List<DataModel.Page> GetPageList(Guid idSite, bool detach = false)
{
var results = from p in DataContext.Pages
where p.idSite == idSite
select p;
if (results.Count() > 0)
{
if (detach)
{
List<DataModel.Page> retValue = new List<DataModel.Page>();
foreach (var result in results)
{
DataContext.Detach(result);
retValue.Add(result);
}
return retValue;
}
else
return results.ToList();
}
else
return new List<DataModel.Page>();
}
I have just successfully tested this code.
It may be that in your case your Message object is in a different assembly? The overriden Property SupportedTypes is returning everything ONLY in its own Assembly so when serialize is called the JavaScriptSerializer defaults to the standard JavaScriptConverter.
You should be able to verify this debugging.
Your error occured due to some "Reference" classes generated by EF for some entities with 1:1 relations and that the JavaScriptSerializer failed to serialize.
I've used a workaround by adding a new condition :
!p.Name.EndsWith("Reference")
The code to get the complex properties looks like this :
var complexProperties = from p in type.GetProperties()
where p.CanWrite &&
p.CanRead &&
!p.Name.EndsWith("Reference") &&
!_builtInTypes.Contains(p.PropertyType) &&
!_processedObjects.Contains(p.GetValue(obj, null)
== null
? 0
: p.GetValue(obj, null).GetHashCode())
select p;
Hope this help you.
I had a similar problem with pushing my view via Ajax to UI components.
I also found and tried to use that code sample you provided. Some problems I had with that code:
SupportedTypes wasn't grabbing the types I needed, so the converter wasn't being called
If the maximum depth is hit, the serialization would be truncated
It threw out any other converters I had on the existing serializer by creating its own new JavaScriptSerializer
Here are the fixes I implemented for those issues:
Reusing the same serializer
I simply reused the existing serializer that is passed into Serialize to solve this problem. This broke the depth hack though.
Truncating on already-visited, rather than on depth
Instead of truncating on depth, I created a HashSet<object> of already seen instances (with a custom IEqualityComparer that checked reference equality). I simply didn't recurse if I found an instance I'd already seen. This is the same detection mechanism built into the JavaScriptSerializer itself, so worked quite well.
The only problem with this solution is that the serialization output isn't very deterministic. The order of truncation is strongly dependent on the order that reflections finds the properties. You could solve this (with a perf hit) by sorting before recursing.
SupportedTypes needed the right types
My JavaScriptConverter couldn't live in the same assembly as my model. If you plan to reuse this converter code, you'll probably run into the same problem.
To solve this I had to pre-traverse the object tree, keeping a HashSet<Type> of already seen types (to avoid my own infinite recursion), and pass that to the JavaScriptConverter before registering it.
Looking back on my solution, I would now use code generation templates to create a list of the entity types. This would be much more foolproof (it uses simple iteration), and have much better perf since it would produce a list at compile time. I'd still pass this to the converter so it could be reused between models.
My final solution
I threw out that code and tried again :)
I simply wrote code to project onto new types ("ViewModel" types - in your case, it would be service contract types) before doing my serialization. The intention of my code was made more explicit, it allowed me to serialize just the data I wanted, and it didn't have the potential of slipping in queries on accident (e.g. serializing my whole DB).
My types were fairly simple, and I didn't need most of them for my view. I might look into AutoMapper to do some of this projection in the future.
I have the following extension method
public static class ListExtensions
{
public static IEnumerable<T> Search<T>(this ICollection<T> collection, string stringToSearch)
{
foreach (T t in collection)
{
Type k = t.GetType();
PropertyInfo pi = k.GetProperty("Name");
if (pi.GetValue(t, null).Equals(stringToSearch))
{
yield return t;
}
}
}
}
What it does is by using reflection, it finds the name property and then filteres the record from the collection based on the matching string.
This method is being called as
List<FactorClass> listFC = new List<FactorClass>();
listFC.Add(new FactorClass { Name = "BKP", FactorValue="Book to price",IsGlobal =false });
listFC.Add(new FactorClass { Name = "YLD", FactorValue = "Dividend yield", IsGlobal = false });
listFC.Add(new FactorClass { Name = "EPM", FactorValue = "emp", IsGlobal = false });
listFC.Add(new FactorClass { Name = "SE", FactorValue = "something else", IsGlobal = false });
List<FactorClass> listFC1 = listFC.Search("BKP").ToList();
It is working fine.
But a closer look into the extension method will reveal that
Type k = t.GetType();
PropertyInfo pi = k.GetProperty("Name");
is actually inside a foreach loop which is actually not needed. I think we can take it outside the loop.
But how?
PLease help. (C#3.0)
Using reflection in this way is ugly to me.
Are you sure you need a 100% generic "T" and can't use a base class or interface?
If I were you, I would consider using the .Where<T>(Func<T, Boolean>) LINQ method instead of writing your own Search function.
An example use is:
List<FactorClass> listFC1 = listFC.Where(fc => fc.Name == "BKP").ToList();
public static IEnumerable<T> Search<T>(this ICollection<T> collection, string stringToSearch)
{
Type k = typeof(T);
PropertyInfo pi = k.GetProperty("Name");
foreach (T t in collection)
{
if (pi.GetValue(t, null).Equals(stringToSearch))
{
yield return t;
}
}
}
There's a couple of things you could do -- first you could institute a constraint on the generic type to an interface that has a name property. If it can only take a FactorClass, then you don't really need a generic type -- you could make it an extension to an ICollection<FactorClass>. If you go the interface route (or with the non-generic version), you can simply reference the property and won't have a need for reflection. If, for some reason, this doesn't work you can do:
var k = typeof(T);
var pi = k.GetProperty("Name");
foreach (T t in collection)
{
if (pi.GetValue(t, null).Equals(stringToSearch))
{
yield return t;
}
}
using an interface it might look like
public static IEnumerable<T> Search<T>(this ICollection<T> collection, string stringToSearch) where T : INameable
{
foreach (T t in collection)
{
if (string.Equals( t.Name, stringToSearch))
{
yield return t;
}
}
}
EDIT: After seeing #Jeff's comment, this is really only useful if you're doing something more complex than simply checking the value against one of the properties. He's absolutely correct in that using Where is a better solution for that problem.
Just get the type of T
Type k = typeof(T);
PropertyInfo pi = k.GetProperty("Name");
foreach (T t in collection)
{
if (pi.GetValue(t, null).Equals(stringToSearch))
{
yield return t;
}
}