Data Types

2016-10-27 1 min to read Contributors

Note

This documentation is for EF Core. For EF6.x, see Entity Framework 6.

Note

The configuration in this section is applicable to relational databases in general. The extension methods shown here will become available when you install a relational database provider (due to the shared Microsoft.EntityFrameworkCore.Relational package).

Data type refers to the database specific type of the column to which a property is mapped.

Conventions

By convention, the database provider selects a data type based on the CLR type of the property. It also takes into account other metadata, such as the configured Maximum Length, whether the property is part of a primary key, etc.

For example, SQL Server uses datetime2(7) for DateTime properties, and nvarchar(max) for string properties (or nvarchar(450) for string properties that are used as a key).

Data Annotations

You can use Data Annotations to specify an exact data type for the column.

public class Blog
{
    public int BlogId { get; set; }
    [Column(TypeName = "varchar(200)")]
    public string Url { get; set; }
}

Fluent API

You can use the Fluent API to specify an exact data type for the column.

class MyContext : DbContext
{
    public DbSet<Blog> Blogs { get; set; }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Blog>()
            .Property(b => b.Url)
            .HasColumnType("varchar(200)");
    }
}

public class Blog
{
    public int BlogId { get; set; }
    public string Url { get; set; }
}

If you are targeting more than one relational provider with the same model then you probably want to specify a data type for each provider rather than a global one to be used for all relational providers.

        modelBuilder.Entity<Blog>()
            .Property(b => b.Url)
            .ForSqlServerHasColumnType("varchar(200)");