I am stating out with entity framework. I have created my ADO.NET Entity Model and mapped the entities to a local SQL CE database file (all done via the wizards). I have created a unit test to test the data access and see how things work. The test executes fine and without any exceptions. However, no new row is generated in the database. Please Help!!!
public void TestCreateRelationshipType()
{
using (var c = new TenderModelEntities())
{
IList<RelationshipType> types = c.RelationshipTypes.ToList<RelationshipType>();
int num1 = types.Count();
RelationshipType type = new RelationshipType();
type.Description = "New Client";
c.AddToRelationshipTypes(type);
c.SaveChanges();
IList<RelationshipType> types2 = c.RelationshipTypes.ToList<RelationshipType>();
int num2 = types2.Count();
Assert.AreEqual(num1 + 1, num2);
}
}
New row is added to the database because you call the SaveChanges() function. When you call this on your datacontext, the changes are passed on to the database.
If you don't want to make any changes to the database, just comment out this section like below
// c.SaveChanges();
Related
The table has to be created dynamically. The table name is dynamic (is sent to API) and columns are static.
Every time api is called, a new table is been created with different name.
Is it possible to do that in Entity Framework? If so - how?
DB is Posstgress.
Thanks
ADO is not the accepted way. I need to do it with Entity Framework.
I tried to write migration that will be activated just when API is called. But it seems that migration can run only when running first.
If you have a bunch of tables with the same columns and you want to switch between them at runtime, you can use SQL Queries.
var blogs = context.Blogs
.FromSql($"SELECT * FROM {QuoteName(tableName)}")
.ToList();
where QuoteName prevents SQL Injection attacks. This one is for SQL Server:
private static string QuoteName(string identifier)
{
var sb = new StringBuilder(identifier.Length + 3, 1024);
sb.Append('[');
foreach (var c in identifier)
{
if (c == ']')
sb.Append(']');
sb.Append(c);
}
sb.Append(']');
return sb.ToString();
}
I'm using EF 6 and MVC 5. I have a method callded MaxScore, see below. I've tested it and it works within my project. I'm new to unit testing so I decided to try it out against this method. When I debug the test I get an error, "Object reference not set to instance of an object". The error points to line 6 in the method below. Any ideas?
Here is my method:
private HandicapSystemContext db = new HandicapSystemContext();
public int MaxScore(double handicap)
{
int _maxScore = 0;
_maxScore = db.AdjustedGrossScores.FirstOrDefault(x => x.MinimiumHandicap <= handicap && x.MaximumHandicap >= handicap).Score;
return _maxScore;
}
Here is my unit test method:
[TestMethod]
public void TestMaxScore()
{
int _maxScore = 0;
Calculation hc = new Calculation();
_maxScore = hc.MaxScore(10);
Assert.AreEqual(_maxScore, 7);
}
To fix the issue, I had to add Entity Framewwork (Using NuGet) to the Test Project. I added a connectionstring to the app.config file. Since I'm using Code First and dropping and regenerating the database on model changes, I had to copy the localDB files to the /bin/Debug/ folder. I will have to recopy the database every time the database changes until I get to a solid state and switch over to a Sql Server database.
I'm working on a MVC3 application and i'm using the Entity Framework linked to an Oracle database (11G R2).
I'm encountering an issue when i'm trying to use a single object context inside a TransactionScope.
Here is the code :
using (TransactionScope scope = new TransactionScope())
{
using (Entities context = new Entities())
{
// Right insert
T_RIGRIGHT entity1 = new T_RIGRIGHT()
{
RIGCODE = "test1",
RIGINSERTLOGIN = "aco",
RIGINSERTDATE = DateTime.Now,
RIGUPDATELOGIN = "aco",
RIGUPDATEDATE = DateTime.Now
};
context.AddToT_RIGRIGHT(entity1);
context.SaveChanges();
// Right/Profile insert
T_RIPRIGHTPROFILE entity2 = new T_RIPRIGHTPROFILE()
{
PROID = 3,
RIGID = entity1.RIGID,
RIPINSERTLOGIN = "aco",
RIPINSERTDATE = DateTime.Now,
RIPUPDATELOGIN = "aco",
RIPUPDATEDATE = DateTime.Now
};
context.AddToT_RIPRIGHTPROFILE(entity2);
context.SaveChanges(); // SaveChanges fails due to the FK constraint on table
}
scope.Complete();
}
Let me explain the code...
First I create an entity called entity1 as a T_RIGRIGHT element.
The I instanciate a T_RIPRIGHTPROFILE element that uses the id of the T_RIGRIGHT element created before.
The execution fails on the second context.SaveChanges() and the exception concerns the Foreign Key constraint on the table T_RIPRIGHTPROFILE (requires a T_RIGRIGHT).
Hope my explanations are clear enough
Is there any way to make it works ?
P.S. : I apologize for my english as it's not my native language.
You are trying to assign the FK entity1.RIGID of an entity that has not been committed to the DB:
RIGID = entity1.RIGID,
If you look at entity1 closely you will see that RIGID is 0 by default - instead you should set the navigation property representing the FK relationship:
RIG = entity1,
This will enable EF to properly relate these entities, for this entity1 does not have to be committed to the DB yet, so you do not even need the extra SaveChanges() call.
Also in your scenario you do not need a TransactionScope - EF uses a transaction internally already in SaveChanges() - based on the suggested changes you only need one SaveChanges() call and hence no outer transaction scope is needed.
I understand stored procedures mapping is not supported by my understanding is that I should be able to call stored procedures.
I have quite a few complex stored procedures and with the designer I could create a complex type and I was all good.
Now in code first let's suppose I have the following stored procedure, just put together something silly to give an idea. I want to return a student with 1 address.
In code I have A Student and Address Entity. But no StudentAddressEntity as it's a link table.
I have tried the following but I get an error
Incorrect syntax near '."}
System.Data.Common.DbException {System.Data.SqlClient.SqlException}
ALTER Procedure [dbo].[GetStudentById]
#StudentID int
AS
SELECT *
FROM Student S
left join StudentAddress SA on S.Studentid = sa.studentid
left join Address A on SA.AddressID = A.AddressID
where S.StudentID = #StudentID
C# code:
using (var ctx = new SchoolContext())
{
var student = ctx.Database.SqlQuery<Student>("GetStudentById,#StudentID",
new SqlParameter("StudentID", id));
}
Any examples out there how to call sp and fill a complexType in code first, using out parameters etc.. Can I hook into ADO.NET?
Trying just an SP that returns all students with no parameters I get this error
System.SystemException = Cannot create a value for property
'StudentAddress' of type
'CodeFirstPrototype.Dal.Address'. Only
properties with primitive types are
supported.
Is it because I have in a way ignore the link table?
Any suggestions?
I believe that your exception actually is:
Incorrect syntax near ','.
because this is invalid statement: "GetStudentById,#StudentID". It should be without comma: "GetStudentById #StudentID".
The problem with stored procedures in EF is that they don't support loading navigation properties. EF will materialize only the main entity and navigation properties will not be loaded. This is solved for example by EFExtensions. EFExtensions are for ObjectContext API so you will have to check if it is also usable for DbContext API.
Using EFExtentions it will look something like
using (var context = new SchoolContext())
{
var command = context.CreateStoreCommand("GetStudentById", CommandType.StoredProcedure,
new SqlParameter("StudentID", id));
using (command.Connection.CreateConnectionScope())
using (var reader = command.ExecuteReader())
{
// use the reader to read the data
// my recommendation is to create a Materializer using EFExtensions see
// http://blogs.msdn.com/b/meek/archive/2008/03/26/ado-entity-framework-stored-procedure-customization.aspx
// ex
var student = Student.Materializer.Materialize(reader).SingleOrDefault();
return student;
}
}
I'm currently working on a project which is using EF Code First with POCOs. I have 5 POCOs that so far depends on the POCO "User".
The POCO "User" should refer to my already existing MemberShip table "aspnet_Users" (which I map it to in the OnModelCreating method of the DbContext).
The problem is that I want to take advantage of the "Recreate Database If Model changes" feature as Scott Gu shows at: http://weblogs.asp.net/scottgu/archive/2010/07/16/code-first-development-with-entity-framework-4.aspx - What the feature basically does is to recreate the database as soon as it sees any changes in my POCOs. What I want it to do is to Recreate the database but to somehow NOT delete the whole Database so that aspnet_Users is still alive. However it seems impossible as it either makes a whole new Database or replaces the current one with..
So my question is: Am I doomed to define my database tables by hand, or can I somehow merge my POCOs into my current database and still take use of the feature without wipeing it all?
As of EF Code First in CTP5, this is not possible. Code First will drop and create your database or it does not touch it at all. I think in your case, you should manually create your full database and then try to come up with an object model that matches the DB.
That said, EF team is actively working on the feature that you are looking for: altering the database instead of recreating it:
Code First Database Evolution (aka Migrations)
I was just able to do this in EF 4.1 with the following considerations:
CodeFirst
DropCreateDatabaseAlways
keeping the same connection string and database name
The database is still deleted and recreated - it has to be to for the schema to reflect your model changes -- but your data remains intact.
Here's how: you read your database into your in-memory POCO objects, and then after the POCO objects have successfully made it into memory, you then let EF drop and recreate the database. Here is an example
public class NorthwindDbContextInitializer : DropCreateDatabaseAlways<NorthindDbContext> {
/// <summary>
/// Connection from which to ead the data from, to insert into the new database.
/// Not the same connection instance as the DbContext, but may have the same connection string.
/// </summary>
DbConnection connection;
Dictionary<Tuple<PropertyInfo,Type>, System.Collections.IEnumerable> map;
public NorthwindDbContextInitializer(DbConnection connection, Dictionary<Tuple<PropertyInfo, Type>, System.Collections.IEnumerable> map = null) {
this.connection = connection;
this.map = map ?? ReadDataIntoMemory();
}
//read data into memory BEFORE database is dropped
Dictionary<Tuple<PropertyInfo, Type>, System.Collections.IEnumerable> ReadDataIntoMemory() {
Dictionary<Tuple<PropertyInfo,Type>, System.Collections.IEnumerable> map = new Dictionary<Tuple<PropertyInfo,Type>,System.Collections.IEnumerable>();
switch (connection.State) {
case System.Data.ConnectionState.Closed:
connection.Open();
break;
}
using (this.connection) {
var metaquery = from p in typeof(NorthindDbContext).GetProperties().Where(p => p.PropertyType.IsGenericType)
let elementType = p.PropertyType.GetGenericArguments()[0]
let dbsetType = typeof(DbSet<>).MakeGenericType(elementType)
where dbsetType.IsAssignableFrom(p.PropertyType)
select new Tuple<PropertyInfo, Type>(p, elementType);
foreach (var tuple in metaquery) {
map.Add(tuple, ExecuteReader(tuple));
}
this.connection.Close();
Database.Delete(this.connection);//call explicitly or else if you let the framework do this implicitly, it will complain the connection is in use.
}
return map;
}
protected override void Seed(NorthindDbContext context) {
foreach (var keyvalue in this.map) {
foreach (var obj in (System.Collections.IEnumerable)keyvalue.Value) {
PropertyInfo p = keyvalue.Key.Item1;
dynamic dbset = p.GetValue(context, null);
dbset.Add(((dynamic)obj));
}
}
context.SaveChanges();
base.Seed(context);
}
System.Collections.IEnumerable ExecuteReader(Tuple<PropertyInfo, Type> tuple) {
DbCommand cmd = this.connection.CreateCommand();
cmd.CommandText = string.Format("select * from [dbo].[{0}]", tuple.Item2.Name);
DbDataReader reader = cmd.ExecuteReader();
using (reader) {
ConstructorInfo ctor = typeof(Test.ObjectReader<>).MakeGenericType(tuple.Item2)
.GetConstructors()[0];
ParameterExpression p = Expression.Parameter(typeof(DbDataReader));
LambdaExpression newlambda = Expression.Lambda(Expression.New(ctor, p), p);
System.Collections.IEnumerable objreader = (System.Collections.IEnumerable)newlambda.Compile().DynamicInvoke(reader);
MethodCallExpression toArray = Expression.Call(typeof(Enumerable),
"ToArray",
new Type[] { tuple.Item2 },
Expression.Constant(objreader));
LambdaExpression lambda = Expression.Lambda(toArray, Expression.Parameter(typeof(IEnumerable<>).MakeGenericType(tuple.Item2)));
var array = (System.Collections.IEnumerable)lambda.Compile().DynamicInvoke(new object[] { objreader });
return array;
}
}
}
This example relies on a ObjectReader class which you can find here if you need it.
I wouldn't bother with the blog articles, read the documentation.
Finally, I would still suggest you always back up your database before running the initialization. (e.g. if the Seed method throws an exception, all your data is in memory, so you risk your data being lost once the program terminates.) A model change isn't exactly an afterthought action anyway, so be sure to back your data up.
One thing you might consider is to use a 'disconnected' foreign key. You can leave the ASPNETDB alone and just reference the user in your DB using the User key (guid). You can access the logged in user as follows:
MembershipUser currentUser = Membership.GetUser(User.Identity.Name, true /* userIsOnline */);
And then use the User's key as a FK in your DB:
Guid UserId = (Guid) currentUser.ProviderUserKey ;
This approach decouples your DB with the ASPNETDB and associated provider architecturally. However, operationally, the data will of course be loosely connected since the IDs will be in each DB. Note also there will be no referential constraints, whcih may or may not be an issue for you.