Can I add extension methods to an existing static class?

I’m a fan of extension methods in C#, but haven’t had any success adding an extension method to a static class, such as Console.

For example, if I want to add an extension to Console, called ‘WriteBlueLine’, so that I can go:

I tried this by adding a local, public static method, with Console as a ‘this’ parameter… but no dice!

This didn’t add a ‘WriteBlueLine’ method to Console… am I doing it wrong? Or asking for the impossible?

Asked on April 7, 2016 in C#.
Add Comment
1 Answer(s)

The following was rejected as an edit to tvanfosson’s answer. I was asked to contribute it as my own answer. I used his suggestion and finished the implementation of a ConfigurationManager wrapper. In principle I simply filled out the ... in tvanfosson’s answer.

No. Extension methods require an instance of an object. You can
however, write a static wrapper around the ConfigurationManager
interface. If you implement the wrapper, you don’t need an extension
method since you can just add the method directly.

public static class ConfigurationManagerWrapper
{
    public static NameValueCollection AppSettings
    {
        get { return ConfigurationManager.AppSettings; }
    }

    public static ConnectionStringSettingsCollection ConnectionStrings
    {
        get { return ConfigurationManager.ConnectionStrings; }
    }

    public static object GetSection(string sectionName)
    {
        return ConfigurationManager.GetSection(sectionName);
    }

    public static Configuration OpenExeConfiguration(string exePath)
    {
        return ConfigurationManager.OpenExeConfiguration(exePath);
    }

    public static Configuration OpenMachineConfiguration()
    {
        return ConfigurationManager.OpenMachineConfiguration();
    }

    public static Configuration OpenMappedExeConfiguration(ExeConfigurationFileMap fileMap, ConfigurationUserLevel userLevel)
    {
        return ConfigurationManager.OpenMappedExeConfiguration(fileMap, userLevel);
    }

    public static Configuration OpenMappedMachineConfiguration(ConfigurationFileMap fileMap)
    {
        return ConfigurationManager.OpenMappedMachineConfiguration(fileMap);
    }

    public static void RefreshSection(string sectionName)
    {
        ConfigurationManager.RefreshSection(sectionName);
    }
}
Answered on April 7, 2016.
Add Comment

Your Answer

By posting your answer, you agree to the privacy policy and terms of service.