Question

I have a string

String input = "nbfs;jlt;\"";

With this string I use .Contains<>()

if (input.Contains<String>("nbfs;jlt;"))
{
    Console.WriteLine("True");
}

also

 if (input.Contains("nbfs;jlt;"))
    {
        Console.WriteLine("True");
    }

does not work.
Why does the above if statement return false?

Answer 1

input.Contains<String>("nbfs;jlt;") is expecting an enumeration of strings.

use: input.Contains("nbfs;jlt;")

EDIT
In response to the many comments, the .Contains<T> method will not compile on a standard string:

string input = "nbfs;jlt;";
input.Contains<String>("nbfs;jlt;") // this will never compile

The .Contains<T> method is expecting some type of enumerable input such as the following to compile:

input.Select( x => x.ToString() ).Contains<String>( "nbfs;jlt;" )

Given that the OP is saying the code compiles, I would suggest opening a new Console Project and start from scratch. And type everything, do not copy/paste.

On a side note: There may be some odd entity characters hidden when you copy/paste from files, so that may be one reason why the Contains method will not work on your string.

Edit 2
This will compile and return true based on your sample strings. Copy/Paste this into a console app and be sure not to include any assemblies other than the default ones with the Console app:

string input = "nbfs;jlt;\"";

bool isContained = input.Contains( "nbfs;jlt;" );

Console.WriteLine( isContained );