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

For me this message was because of misunderstanding for TypeName in Column attribute.

Column Attribute: [Column (string name, Properties:[Order = int],[TypeName = string])

name: Name of a column in a db table.
Order: Order of a column, starting with zero index. (Optional)
TypeName: Data type of a column. (Optional)

This TypeName must be only name of the type and must not include precision or scale or length and any other thing. For example following will cause an error

[Column(TypeName = "nvarchar(600)")]

while below one will work fine however you might want to have specific size of the column and for that one way is to use fluent API

[Column(TypeName = "nvarchar")]

Answer 2

For me it helped, when switched class project to Set as startup project

Answer 3

I had a bug where I got a System.InvalidOperationException with the message Sequence contains no matching element because I had an incorrect string value being passed to .HasColumnType() in my table configuration.

Answer 4

Entity Framework throws this exception if the column type is invalid. For example:

// This will throw an error. There is no such type name.
[Column(TypeName = "Invalid")]
public string Column1 { get; set; }

// Works.
[Column(TypeName = "varchar")]
public string Column1 { get; set; }

See these examples:

• Example 1
• Example 2
• Other examples in comments.