What does "Property where class => someFunction" mean in C#

Question

I'm browsing through the EF7 code on Github and found a line that looks like this:

public virtual DbSet<TEntity> Set<TEntity>() where TEntity : class => _setInitializer.Value.CreateSet<TEntity>(this);

I have seen that syntax before on a class level, like this:

public class SomeClass<T> where T : class

Which says that T should be of type class. But the line from the EF7 source confuses me. I'm not sure what it does.

Answer 1

It's an expression-bodied member, a new syntax in C# 6.

It's a method, not a property. C# doesn't allow generic properties.

It's the same as

public virtual DbSet<TEntity> Set<TEntity>() where TEntity : class
{
    return _setInitializer.Value.CreateSet<TEntity>(this);
}

Answer 2

This syntax is a bit confusing indeed, but actually the lambda construct here has nothing to do with generic constraints. It's just an Expression-Bodied Method that happened to have a generic constraint.

You can think of it as:

public virtual DbSet<TEntity> Set<TEntity>() where TEntity : class
{
    return _setInitializer.Value.CreateSet<TEntity>(this);
}

See Roslyn Wiki

Answer 3

It's a C# 6.0 feature called Expression Bodied Method.

Read here about it.

The code is equivalent to:

public virtual DbSet<TEntity> Set<TEntity>() where TEntity : class 
{
    return _setInitializer.Value.CreateSet<TEntity>(this);
}