I have been trying to get reference in the Microsoft Developer website about what the function of the : really is but I cant find it because it seems that it is neither a keyword or a operator so what is the function of the colon in C#? Also I have seen it being applied to a Method how does that function?.
Colons are used in a dozen fundamentally different places (that I can think of, with the help of everyone in the comments):
Separating a class name from its base class / interface implementations in class definitions
public class Foo : Bar { }
Specifying a generic type constraint on a generic class or method
public class Foo<T> where T : Bar { }
public void Foo<T>() where T : Bar { }
Indicating how to call another constructor on the current class or a base class's constructor prior to the current constructor
public Foo() : base() { }
public Foo(int bar) : this() { }
Specifying the global namespace (as C. Lang points out, this is the namespace alias qualifier)
global::System.Console
Specifying attribute targets
[assembly: AssemblyVersion("1.0.0.0")]
Specifying parameter names
Console.WriteLine(value: "Foo");
As part of a ternary expression
var result = foo ? bar : baz;
As part of a case or goto label
switch(foo) { case bar: break; }
goto Bar;
Foo: return true;
Bar: return false;
Since C# 6, for formatting in interpolated strings
Console.WriteLine($"{DateTime.Now:yyyyMMdd}");
Since C# 7, in tuple element names
var foo = (bar: "a", baz: "b");
Console.WriteLine(foo.bar);
In all these cases, the colon is not used as an operator or a keyword (with the exception of ::). It falls into the category of simple syntactic symbols, like [] or {}. They are just there to let t