C# supports single inheritance, however they do support multiple 'interface' inheritance:

Here's a sample demonstrating the same:

//Single Inheritance

public class A
{
    public A() { }
}

public class B : A
{
    public B() { }
} 


//Multiple Interface Inheritance

interface IComparable
{
    int CompareTo(object obj);
}

interface ISomethingElse
{
    int EqualTo();
}


public class Z :  IComparable, ISomethingElse
{
    public int CompareTo(object obj)
    {
        // implementation code goes here 
    }


    public int EqualTo()
    {
        // implementation code goes here 
    }
}