Calculated column in EF Code First

In EF6, you can just configure the mapping setting to ignore a calculated property, like this:

Define the calculation on the get property of your model:

public class Person
{
    // ...
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public string FullName => $"{FirstName} {LastName}";
}

Then set it to ignore on the model configuration

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    //...
    modelBuilder.Entity<Person>().Ignore(x => x.FullName)
}

public string ChargePointText { get; set; }

public class FirstTable 
{
    [Key]
    public int UserID { get; set; }

    [DatabaseGenerated(DatabaseGeneratedOption.Computed)]      
    public string Summ 
    {
        get { return /* do your sum here */ }
        private set { /* needed for EF */ }
    }
}

References:

• Bug in EF 4.1 DatabaseGeneratedOption.Computed
• Calculated Columns in Entity Framework Code First Migrations
• Working with Computed Columns

As of 2019, EF core allows you to have computed columns in a clean way with the fluent API:

Suppose that DisplayName is the computed column you want to define, you have to define the property as usual, possibly with a private property accessor to prevent assigning it

public class Person
{
    public int PersonId { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
    // this will be computed
    public string DisplayName { get; private set; }
}

Then, in the model builder, address it with the column definition:

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    modelBuilder.Entity<Person>()
        .Property(p => p.DisplayName)
        // here is the computed query definition
        .HasComputedColumnSql("[LastName] + ', ' + [FirstName]");
}

For further information, have a look at MSDN.

You can create computed columns in your database tables. In the EF model you just annotate the corresponding properties with the DatabaseGenerated attribute:

[DatabaseGenerated(DatabaseGeneratedOption.Computed)]
public double Summ { get; private set; } 

Or with fluent mapping:

modelBuilder.Entity<Income>().Property(t => t.Summ)
    .HasDatabaseGeneratedOption(DatabaseGeneratedOption.Computed)

As suggested by Matija Grcic and in a comment, it's a good idea to make the property private set, because you'd probably never want to set it in application code. Entity Framework has no problems with private setters.

Note: For EF .NET Core you should to use ValueGeneratedOnAddOrUpdate because HasDatabaseGeneratedOption doesnt exists, e.g.:

modelBuilder.Entity<Income>().Property(t => t.Summ)
    .ValueGeneratedOnAddOrUpdate()