Creating string index with Code first

Question

I'm using Entity Framework 6.1 code-first and my domain model is below.

class Item {     [Index]     public string CreatedBy { set; get; } }  

When I use update-database for migration, I get the following error. However as far as I researched [Index] should work as annotation to string.

Column 'CreatedBy' in table 'dbo.Items' is of a type that is invalid for use as a key column in an index.

Answer 1

Usually you get this error when you use a VARCHAR(Max) try using:

[Column(TypeName = "VARCHAR")] [StringLength(n)] [Index] public string CreatedBy { set; get; } 

where n is between 1 and 450.

Answer 2

If you use EntityTypeConfiguration aka mappings :

public class MyPocoEntitiyTypeConfig<T> : EntityTypeConfiguration<T> where T:class {  }  public class MyPocoEnt {     public virtual string MyProp { get; set; } }  public class MyPocoEntMapping : MyPocoEntitiyTypeConfig<MyPocoEnt> {     public MyPocoEntMapping()     {             Property(x => x.MyProp).HasMaxLength(300);             Property(x => x.MyProp).HasColumnAnnotation("Index", new IndexAnnotation(new IndexAttribute("MyProp") { IsUnique = true }));         }     } }