Switch Expression in C#

[ShervanN]

Hello,

How can I fix this error?

Error CS0118 'myString' is a variable but is used like a type

   static string Pattern(string myString)
    {
        return myString switch
        {
            myString.StartsWith("A") => "First",
        };
    }

[LuohuaRain]

static string Pattern(string myString)
{
	return myString[0] switch
	{
		'A' => "first",
	};
}

[ShervanN]

Thank you, But I'd like to check the following string instead of the character.

  static string Pattern(string myString)
    {
        return myString switch
        {
            myString.StartsWith("TEST") => "first",
        };
    }

[christiannagel]

@ShervanN , @LuohuaRain is correct with his answer. The issue with your code is: with the switch expression you need a pattern, such as a const pattern. If you want to check for the const "TEST", you can do this in the same way:

static string Pattern(string myString)
{
    return myString switch
    {
        "TEST" => "first",
        _ => "second"
    };
}

In case it's not a const you need, you can use when and use a type pattern:

static string Pattern(string myString, string match)
{
    return myString switch
    {
        string s when s.StartsWith(match) => "first",
        _ => "second"
    };
}

[ShervanN]

Thanks