Sequence contains no matching element - EntityFramework

Question

I\'m using EF 6.1.0 and was creating a WCF Service.

First I created a Class Library containing my entities, Mappers and Context for initializing EF. I\'ve also creat

Answer 1

I got caught with this one because I referenced the reference property instead of the Id property.

        var t = modelBuilder.Entity<CyDocument>();
        t.HasIndex(b => b.DocTypeId);

Answer 2

I got the same error message when I had renamed my Member model to Student and I had a navigation property in some other class as:

public IList<Student> Members { get; set; }

I changed that to:

public IList<Student> Students { get; set; }

and the problem was resolved!

Answer 3

I got this error while defining Table-Per-Type Inheritance with Fluent API (as a class deriving from EntityTypeConfiguration<T>) and mistakenly redefined field that was already defined in base class configuration (and both were exactly the same). I was using EntityFramework 6.2.0 nuget package.

Answer 4

I was also getting same error while adding migration or updating database.

The reason was I was using wrong column type

[Column("ImageType", TypeName = "varchar(20)")]
public string ImageType
{
     get;
     set;
}

But when I removed 20 from varchar it started working for me

[Column("ImageType", TypeName = "varchar")]
public string ImageType
{
    get;
    set;
}

Answer 5

Yup. Caught me as well because in a moment of distraction I put the literal long in there for a bigint column i.e. HasColumnType("long")- can you believe it?! What a clown!

Generators generally create your EF classes properly, but if you're not able to or don't want to use one then you could use a static class with some static string fields on them so that you can intellisense it quite nicely:

public static class DatabaseColumnTypes
{
    /// <summary>
    /// Use this for 'boolean' values.
    /// </summary>
    public static string BitColumn = "bit";

    /// <summary>
    /// Use this for 'byte' values.
    /// </summary>
    public static string TinyIntColumn = "tinyint";

    /// <summary>
    /// Use this for 'long' values.
    /// </summary>
    public static string BigIntColumn = "bigint";

    /// <summary>
    /// Use this for 'string' values.
    /// </summary>
    public static string VarcharColumn = "varchar";

    // etc
}

Now you can do HasColumnType( DatabaseColumnTypes.BigIntColumn )

I know, I know, this is lazy, I should remember these types but every so often I find myself on Stack Overflow looking it up and this just saves time…

Answer 6

I just experienced the same problem. The Code First from database wizard generated one of the columns as [Column(TypeName = "date")].

Calling .saveChanges() resulted in the Sequence contains no elements.

After changing the defined column to [DataType(DataType.DateTime)] it worked as expected.