Question

What is happening below?

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

public class DotNetPad
{
    public static void Main(string[] args)
    {
        int i = 10;
        string k = "Test";
        Console.WriteLine(i+k);
        Console.WriteLine(k+i);
    }
}

i is being converted to string in both cases. I am confusing myself with the idea of operator precedence (although this example doesn’t show much of that) and evaluation direction. Sometimes evaluation happens from left-to-right or vice versa. I don’t exactly know the science of how the expression is evaluated…

Why is i converted to string in the above example, and not actually giving a compilation error?

Answer 1

From the C# spec – section 7.7.4 Addition operator:

String concatenation:

string operator +(string x, string y);
string operator +(string x, object y);
string operator +(object x, string y);

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.