I know that I can do something like this:
var test = new { FirstName = string.Empty, LastName = string.empty };
But I don't if there's is a way to do it dynamically, let's say:
var test = new {};
if (condition) {
test.Property = string.Empty;
}
Let's say I Have this:
string[] names =
{
"eder",
"quiñones",
"quoe840629",
"3301"
};
var anonymous = new {};
foreach (string name in names) {
// Create anonymous types...
}
Any suggestions?
~ Eder Quiñones
You can do:
var test = new { FirstName = (condition ? string.Emtpy : "other") };
If you were using c# 4 you could use a dynamic type (ExpandoObject).
Related
On the Dynamic LINQ website there's an example using the Like function.
I am unable to get it to work with ef core 3.1
[Test]
public void DynamicQuery()
{
using var context = new SamDBContext(Builder.Options);
var config = new ParsingConfig { ResolveTypesBySimpleName = true };
var lst = context.Contacts.Where(config, "DynamicFunctions.Like(FirstName, \"%Ann%\")".ToList();
lst.Should().HaveCountGreaterThan(1);
}
Example from the Dynamic LINQ website
var example1 = Cars.Where(c => EF.Functions.Like(c.Brand, "%t%"));
example1.Dump();
var config = new ParsingConfig { ResolveTypesBySimpleName = true };
var example2 = Cars.Where(config, "DynamicFunctions.Like(Brand, \"%t%\")");
example2.Dump();
Looks like my code. But I am getting the following error
System.Linq.Dynamic.Core.Exceptions.ParseException : No property or field 'DynamicFunctions' exists in type 'Contact'
you don't need the ResolveTypesBySimpleName, implement your wont type provider.
The piece below people to use PostgreSQL ILike with unnaccent
public class LinqCustomProvider : DefaultDynamicLinqCustomTypeProvider
{
public override HashSet<Type> GetCustomTypes()
{
var result = base.GetCustomTypes();
result.Add(typeof(NpgsqlFullTextSearchDbFunctionsExtensions));
result.Add(typeof(NpgsqlDbFunctionsExtensions));
result.Add(typeof(DbFunctionsExtensions));
result.Add(typeof(DbFunctions));
result.Add(typeof(EF));
return result;
}
}
// ....
var expressionString = $"EF.Functions.ILike(EF.Functions.Unaccent(People.Name), \"%{value}%\")";
var config = new ParsingConfig()
{
DateTimeIsParsedAsUTC = true,
CustomTypeProvider = new LinqCustomProvider()
};
return query.Where(config, expressionString);
Hope this helps people, took me some time to get this sorted.
My application is ASP.NET MVC 5 / SQL Server.
I am trying to select specific columns from a list based on an array:
First list has 200 columns: Age, Gender, .....
var list1 = _reportRepository.ShowMasteView().ToList();
Second list has 20 columns: Age, Gender, ......
From the view I select the items to be displayed:
string[] lits2 = showColumn.Where(c => c.Value == true).Select(c=> c.Key).ToArray();
I get
To get these two specific columns, I tried
var nList = list1.Select(t2 => lits2.Any(t1 => t2.Contains(t1)));
I get an error
Can not resolve symbol "Contains"
I was able to do it using the following
var keys = "Age,Gender";
var connection =
ConfigurationManager.ConnectionStrings["DALEntities"].ConnectionString;
using (var dataAdapter = new SqlDataAdapter("SELECT " + keys
+ " from dbo.vw_MasterView", connection))
{
var dataTable = new DataTable();
dataAdapter.Fill(dataTable);
dataAdapter.FillSchema(dataTable, SchemaType.Mapped);
return dataTable;
}
Is there a better way in linq?
From my understand it appears you are trying to extract/select a dynamic object that only has the desired properties/columns.
This can be achieved by building a dynamic expression/function to apply to the Select
The following builds an expression based on the model type and the provided properties
static class DynamicExtensions {
public static IQueryable<dynamic> SelectDynamic<TModel>(this IQueryable<TModel> query, ISet<string> propertyNames) {
var selector = query.BuildSelectorFor(propertyNames);
return query.Select(selector);
}
static Expression<Func<TModel, dynamic>> BuildSelectorFor<TModel>(this IQueryable<TModel> query, ISet<string> propertyNames) {
var modelType = typeof(TModel);
var properties = modelType.GetProperties().Where(p => propertyNames.Contains(p.Name));
// Manually build the expression tree for
// the lambda expression v => new { PropertyName = v.PropertyName, ... }
// (TModel v) =>
var parameter = Expression.Parameter(modelType, "v");
// v.PropertyName
var members = properties.Select(p => Expression.PropertyOrField(parameter, p.Name));
var addMethod = typeof(IDictionary<string, object>).GetMethod(
"Add", new Type[] { typeof(string), typeof(object) });
// { { "PropertyName", v.PropertyName}, ... }
var elementInits = members.Select(m =>
Expression.ElementInit(addMethod, Expression.Constant(m.Member.Name), Expression.Convert(m, typeof(object))));
// new ExpandoObject()
var newExpando = Expression.New(typeof(ExpandoObject));
// new ExpandoObject() { { "PropertyName", v.PropertyName}, ... }
var expando = Expression.ListInit(newExpando, elementInits);
// (TModel v) => new ExpandoObject() { { "PropertyName", v.PropertyName}, ... }
var lambdaExpression = Expression.Lambda<Func<TModel, dynamic>>(expando, parameter);
return lambdaExpression;
}
}
This takes advantage of ExpandoObject whose members can be dynamically added and removed at run time.
The following test was used as an example of how the above function is invoked.
[TestMethod]
public void DynamicList() {
var list1 = new List<Person>
{
new Person{ Gender = "Male", Age = 10, FirstName = "Nama1", SampleNumber = 12},
new Person{ Gender = "Male", Age = 12, FirstName = "Nama2", SampleNumber = 13},
new Person{ Gender = "Female", Age = 13, FirstName = "Nama3", SampleNumber = 14},
new Person{ Gender = "Male", Age = 14, FirstName = "Nama4", SampleNumber = 15},
};
var keys = new string[] { "Age", "Gender", };
var nList = list1.AsQueryable().SelectDynamic(new HashSet<string>(keys));
foreach (IDictionary<string, object> row in nList) {
var msg = $"{{ {keys[0]} = {row[keys[0]]}, {keys[1]} = {row[keys[1]]} }}";
Debug.WriteLine(msg);
}
}
and produces the following output
{ Age = 10, Gender = Male }
{ Age = 12, Gender = Male }
{ Age = 13, Gender = Female }
{ Age = 14, Gender = Male }
The dynamic objects can be used in the View and it is a simple matter of calling the desired members.
For example suppose you have a model as follows
public class MyViewModel {
public string MyProperty { get; set; }
public string[] Keys { get; set; }
public List<dynamic> MyDynamicProperty { get; set; }
}
that was populated with data and given to the view
var list1 = _reportRepository.ShowMasteView();
var keys = new string[] { "Age", "Gender", };
var nList = list1.AsQueryable().SelectDynamic(new HashSet<string>(keys));
var viewModel = new MyViewModel {
MyProperty = "Hello World",
MyDynamicProperty = nList.ToList(),
Keys = keys
};
return View(viewModel);
Then in the view you can use the model as desired, casting to get access to members in the expando object.
#model MyViewModel
...
<h2>#Model.MyProperty</h2>
<table>
<tr>
#foreach(string key in Model.Keys) {
<th>#key</th>
}
</tr>
#foreach (IDictionary<string, object> row in Model.MyDynamicProperty) {
<tr>
#foreach(string key in Model.Keys) {
<td>#row[#key]</td>
}
</tr>
}
</table>
I think you just need to use Contains on your list2.
var nList = list1.Where(t => lits2.Contains(t1));
Contains is a method for Lists. The code you had was trying to use it on a string.
If you have two list of a person's class
public class Person
{
public int id { get; set; }
public string name { get; set; }
}
If the lists are as below:
var list1 = new List<Person>
{
new Person{ id = 1, name = "Nama1"},
new Person{ id = 2, name = "Nama2"},
new Person{ id = 3, name = "Nama3"},
new Person{ id = 4, name = "Nama4"},
};
var list2 = new List<Person>
{
new Person{ id = 1, name = "Nama1"},
new Person{ id = 2, name = "Nama2"},
};
You can filter in the following ways
var keys = list2.Select(x => x.id).ToList();
var filter1= list1.Where(x => keys.Contains(x.id)).ToList();
var filter2= list1.Where(x => keys.Contains(x.id)).Select(x => new { x.name }).ToList();
var filter3= list1.Select(x => new
{
id = x.id,
name = x.name,
check = keys.Contains(x.id)
}).Where(x => x.check).ToList();
If you have array of string
you can use below code
array string same
var lis1 = new string[] {"name1", "name2","name3" };
var lis2 = new string[] { "name1" };
You can filter array of string in the following ways
var items1= lis1.Where(x=>lis2.Contains(x)).ToList();
var items= lis1.Select(x=> new { x, check= lis2.Contains(x) }).Where(x=>x.check == true).ToList();
I am using within my code some EF LINQ expressions to keep complex queries over my model in one place:
public static IQueryable<User> ToCheck(this IQueryable<User> queryable, int age, bool valueToCheck = true)
{
return queryable.Where(ToBeReviewed(age, valueToCheck));
}
public static Expression<Func<User, bool>> ToCheck(int age, bool valueToCheck = true)
{
return au => au.Status == UserStatus.Inactive
|| au.Status == UserStatus.Active &&
au.Age.HasValue && au.Age.Value > age;
}
I am then able to use them in queries:
var globalQuery = db.Users.ToCheck(value);
And also in selects:
var func = EntityExtensions.ToCheck(value);
var q = db.Department.Select(d => new
{
OrdersTotal = d.Orders.Sum(o => o.Price),
ToCheck = d.Users.AsQueryable().Count(func),
})
What I am trying to achieve is to actually use the same expression/function within a select, to evaluate it for each row.
var usersQuery = query.Select(au => new {
Id = au.Id,
Email = au.Email,
Status = au.Status.ToString(),
ToBeChecked = ???, // USE FUNCTION HERE
CreationTime = au.CreationTime,
LastLoginTime = au.LastLoginTime,
});
I am pretty that threre would be a way using plain EF capabilities or LINQKit, but can't find it.
Answering my own question :)
As pointed by #ivan-stoev, the use of Linqkit was the solution:
var globalQueryfilter = db.Users.AsExpandable.Where(au => au.Department == "hq");
var func = EntityExtensions.ToCheck(value);
var usersQuery = globalQueryfilter.Select(au => new
{
Id = au.Id,
Email = au.Email,
Status = au.Status.ToString(),
ToBeChecked = func.Invoke(au),
CreationTime = au.CreationTime,
LastLoginTime = au.LastLoginTime,
});
return appUsersQuery;
It's required to use the AsExpandable extension method from Linqkit along with Invoke with the function in the select method.
I want to add one more example:
Expression<Func<AddressObject, string, string>> selectExpr = (n, a) => n == null ? "[no address]" : n.OFFNAME + a;
var result = context.AddressObjects.AsExpandable().Select(addressObject => selectExpr.Invoke(addressObject, "1"));
Also, expression can be static in a helper.
p.s. please not forget to add "using LinqKit;" and use "AsExpandable".
Here's what the required function would look like:
public static Expression<Func<T, T>> GetExpression<T>(string propertyNames) where T : class
{
var properties = propertyNames.Split(
new char[] { ',' },
StringSplitOptions.RemoveEmptyEntries
).ToList();
//need help here
}
Currently I'm doing it like this:
_context.Questions.Select(q =>
new Question() {
QuestionId = q.QuestionId,
QuestionEnglish = q.QuestionEnglish
}
).ToList();
And I want to replace it with:
_context.Questions.Select(GetExpression<Question>("QuestionId, QuestionInEnglish")).ToList();
Any help would be greatly appreciated.
You can do it like this;
public static Func<T, T> GetExpression<T>(string propertyNames)
{
var xParameter = Expression.Parameter(typeof(T), "parameter");
var xNew = Expression.New(typeof(T));
var selectFields = propertyNames.Split(',').Select(parameter => parameter.Trim())
.Select(parameter => {
var prop = typeof(T).GetProperty(parameter);
if (prop == null) // The field doesn't exist
{
return null;
}
var xOriginal = Expression.Property(xParameter, prop);
return Expression.Bind(prop, xOriginal);
}
).Where(x => x != null);
var lambda = Expression.Lambda<Func<T, T>>(Expression.MemberInit(xNew, selectFields), xParameter);
return lambda.Compile();
}
Usage;
var list = new List<Question>{new Question{QuestionEnglish = "QuestionName",QuestionId = 1}};
var result = list.Select(GetExpression<Question>("QuestionId, QuestionEnglish"));
I have this code:
public IEnumerable<SomeClass> GetAvalibleThingies(DateTime startDate, DateTime endDate, int categoryID)
{
if (_entities.Connection.State == System.Data.ConnectionState.Closed)
_entities.Connection.Open();
using (EntityCommand c = new EntityCommand("SomeEntities.GetAvalibleThingies", (EntityConnection)this._entities.Connection))
{
c.CommandType = System.Data.CommandType.StoredProcedure;
EntityParameter paramstartDate = new EntityParameter("startDate", System.Data.DbType.DateTime);
paramstartDate.Direction = System.Data.ParameterDirection.Input;
paramstartDate.Value = startDate;
c.Parameters.Add(paramstartDate);
........
var x = c.ExecuteReader();
return x as IEnumerable<SomeClass>;
};
But I can't get it to return a list of SomeClass. What's needed to do here? I use the entity framework 3.5sp1 one
/M
EntityDataReader is a class similar to SqlDataReader and should be handled in the similar way.
Instead of the lines
var x = c.ExecuteReader();
return x as IEnumerable;
should be something like
List list = new List();
using(EntityDataReader reader = c.ExecuteReader()) {
while(reader.Read()) {
SomeClass item = new SomeClass() {
};
list.Add(item);
}
}
return list;