C# Online Compiler | .NET Fiddle

<no name> by Anonymous

using System;
using System.Collections.Generic;

public class Program
{
	public static void Main()
	{
		var dict = new Dictionary<string, string>();
		dict.Add(null, "cacat");
		
		Console.WriteLine("Hello World");
	}
}

​x
 
using System;
using System.Collections.Generic;
​
public class Program
{
    public static void Main()
    {
        var dict = new Dictionary<string, string>();
        dict.Add(null, "cacat");
        
        Console.WriteLine("Hello World");
    }
}

Run-time exception (line 9): Value cannot be null.
Parameter name: key

Stack Trace:

[System.ArgumentNullException: Value cannot be null.
Parameter name: key]
   at System.ThrowHelper.ThrowArgumentNullException(ExceptionArgument argument)
   at System.Collections.Generic.Dictionary`2.Insert(TKey key, TValue value, Boolean add)
   at Program.Main() :line 9

Last Run:	12:41:59 pm
Compile:	0.136s
Execute:	0s
Memory:	48kb
CPU:	0s

View IL Code