CODEWITHSUNDEEP
c#stringnull
MirlvsMaximvs
MirlvsMaximvs

Reputation: 1483

Why + operator doesn't throw any exception when any null parameters?

Sorry about my ignorance but I've been trying for a long time without a reasonable explication about this: Why a + operator doesn't throw any exception when any parameter is null; for example:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication4
{
    class Program
    {
        static void Main(string[] args) {

            string str = null;
            Console.WriteLine(str + "test");
            Console.ReadKey();
        }
    }
}

Upvotes: 2

Views: 85

Answers (1)

Soner Gönül
Soner Gönül

Reputation: 98868

Because C# compiler translates + operator to String.Concat method in your operation and this method uses empty string "" when you try to concatenate null.

From documentation;

An Empty string is used in place of any null argument.

And from 7.7.4 Addition operator

The binary + operator performs string concatenation when one or both operands are of type string. If an operand of string concatenation is null, an empty string is substituted. Otherwise, any non-string argument is converted to its string representation by invoking the virtual ToString method inherited from type object. If ToString returns null, an empty string is substituted.

Also from reference source;

if (IsNullOrEmpty(str0))
{
     if (IsNullOrEmpty(str1))
     {
         return String.Empty;
     }
     return str1;
}

Upvotes: 8

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