What is the equivalent of a 'friend' keyword in C Sharp?

1. You can use the keyword access modifier internal to declare a type or type member as accessible to code in the same assembly only.

2. You can use the InternalsVisibleToAttribute class defined in System.Rutime.CompilerServices to declare a type as accessible to code in the same assembly or a specified assembly only.

You use the first as you use any other access modifier such as private. To wit:

internal class MyClass {
    ...
}

You use the second as follows:

[assembly:InternalsVisibleTo("MyFriendAssembly", PublicKey="...")]
internal class MyVisibleClass {
    ...
}

Both of these can rightly be considered the equivalent of friend in C#.

Methods that are protected are already available to derived classes.

No, "internal" is not the same as "friend" (at least the C++ 'friend')

friend specifies that this class is only accessible by ONE, particular class.
internal specifies that this class is accessible by ANY class in the assembly.

1. internal is the C# equivalent of the VB.NET friend keyword, as you have guessed (as opposed to a replacement)

2. Usage is as follows

   internal void Function() {}
   internal Class Classname() {}
   internal int myInt;
   internal int MyProperty { get; set; }
   

3. It, basically, is an access modifier that stipulates that the accessibility of the class / function / variable / property marked as internal is as if it were public to the Assembly it is compiled in, and private to any other assemblies