can switch case contain method in c#?

You can do anything in a Case block inside a Switch/Case clause that you can do in any method. Of course, you can't define a class, method, or struct in a Switch/Case block, just as you can't define those inside a standard method (unless you did some very esoteric stuff with reflection or Lambda Expressions, and so forth) ... but, why would you ever want to do that ?

Use of a Switch/Case clause is almost a standard in the classic Calculator example that many .NET books give: for example, if I create a set of Buttons, and set the text of each one of them to some basic calculation, and then assign the same Click EventHandler to all of them:

// assume you have a TextBox, 'tBoxResult, 
// where you want the result of the calculation displayed:
private void CalcBtnClick(object sender, EventArgs e)
{
    Button buttonClicked = sender as Button;

    // make sure we have a valid button !
    if(buttonClicked == null) throw new ArgumentException("argument passed to CalcBtnClick is not Type 'Button");

    // code here to get current operands to be processed,
    // if necessary convert them from strings to double
    // for testing only: assume arguments are in:
    double arg1 = 10.0;
    double arg2 = 20.0;

    switch (buttonClicked.Text)
    {
        case "+":
            // add
            tBoxResult.Text = (arg1 + arg2).ToString();
            break;
        case "-":
            // subtract
            tBoxResult.Text = (arg1 - arg2).ToString();
            break;
        case "*":
            // multiply
            tBoxResult.Text = (arg1 * arg2).ToString();
            break;
    }
}

There is a more "elegant" way to do this using a Dictionary holding Buttons as Keys, and Funcs (methods ... in the form of Lambda Expressions) as Values, but it is a very advanced use of .NET. On request I will demonstrate that here.

A swtich expression or case label must be a bool,char,string,integral,enum only
methods ,any other types cannot be used.

reference :
link [^]