I have a C# code problem with an if and switch statement

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C#

I am going to write a program that will tell the user the number of days in a individual month. The program should allow the user to enter a whole number representing the month (Jan = 1, Feb = 2, etc.). After checking that this is a valid month number (i.e., between 1 and 12), program should then determine the number of days in that month two different times: once using a series of if statements and once using a switch statement.
Place the resulting number of days in two different output Labels.
NOTE: Assume that February always has 28 days.

[EDIT]

private void button1_Click(object sender, EventArgs e)
       {
           int monthNo = 0;
           string[] month = new string[13];
           month[0] = "\0";
           month[1] = "January"; month[2] = "February"; month[3] = "March";
           month[4] = "April"; month[5] = "May"; month[6] = "June";
           month[7] = "July"; month[8] = "August"; month[9] = "September";
           month[10] = "October"; month[11] = "November"; month[12] = "December";

           {


               monthNo = int.Parse(monthNoText.Text);
               if (monthNo <= 0 || monthNo > 12)
               {
                   MessageBox.Show("Invalid Input!!",
                       "Must be 1 to 12!!");

               }

               {
                   switch (monthNo)
                   {
                       case 1:
                       case 3:
                       case 5:
                       case 7:
                       case 8:
                       case 10:
                       case 12:
                           switchText.Text = "31 days";
                           break;
                       case 4:
                       case 6:
                       case 9:
                       case 11:
                           switchText.Text = "30 days";
                           break;
                       case 2:
                           switchText.Text = "28 days";
                           break;
                   }

this is what i got but i need the same info in stch label and if label