Conversion Operator « Operator overloading « Language Basics

You can define conversion operators to specify how your type is converted to other types and how other types are converted to your type.

The following method fragment is a conversion operator from the Text type that converts an instance of string to an instance of Text:


public static explicit operator Text(string str) 
{ 
   return new Word() { MyString = str }; 
}


Text text = (Text)"abc";

We have had to explicitly cast the string to Text, because our conversion operator included the explicit keyword.

You can enable implicit conversion by using the implicit keyword, such as this:


public static implicit operator Text(string str) 
{ 
   return new Text() { MyString = str }; 
}


Text text = (Text)"Hello"; 
Text text = "Hello";

The following example defines and demonstrates implicit and explicit conversion operators for the Text type.


using System;

public class Text
{
    public string MyString
    {
        get;
        set;
    }

    public static explicit operator Text(string str)
    {
        return new Text() { MyString = str };
    }

    public static implicit operator string(Text w)
    {
        return w.MyString;
    }

    public static explicit operator int(Text w)
    {
        return w.MyString.Length;
    }

    public override string ToString()
    {
        return MyString;
    }
}

public class MainClass
{
    static void Main(string[] args)
    {
        Text word1 = new Text() { MyString = "Hello" };
        // Implicitly convert the word to a string. 
        string str1 = word1;
        // Explicitly convert the word to a string. 
        string str2 = (string)word1;
        Console.WriteLine("{0} - {1}", str1, str2);

        // Convert a string to a word. 
        Text word2 = (Text)"Hello";

        // Convert a word to an int. 
        int count = (int)word2;

        Console.WriteLine("Length of {0} = {1}", word2.ToString(), count);
    }
}


Hello - Hello
Length of Hello = 5