Data Types

• 10/27/2016
• 2 minutes to read
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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 .NET 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 a column.

For example the following code configures Url as a non-unicode string with maximum length of 200 and Rating as decimal with precision of 5 and scale of 2.

public class Blog
{
    public int BlogId { get; set; }
    [Column(TypeName = "varchar(200)")]
    public string Url { get; set; }
    [Column(TypeName = "decimal(5, 2)")]
    public decimal Rating { get; set; }
}

Fluent API

You can also use the Fluent API to specify the same data types for the columns.

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

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Blog>(eb =>
        {
            eb.Property(b => b.Url).HasColumnType("varchar(200)");
            eb.Property(b => b.Rating).HasColumnType("decimal(5, 2)");
        });
    }
}

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