Question

Getting an error of :

Error   1   'string RadioGroupTester.Form1.chkReceipt_CheckedChanged(object, System.EventArgs)' has the wrong return type

When I compile a very simple program to understand radio and check box controls.

Here’s the code for the form is as follows:

    private string rdoMastercard_CheckedChanged(object sender, EventArgs e)
    {
        if (rdoMastercard.Checked)
            return "You have selected Mastercard";
        else
            return "You have selected Visa";
    }

    private string chkReceipt_CheckedChanged(object sender, EventArgs e)
    {
        if (chkReceipt.Checked)
            return "You will receive a receipt";
        else
            return "You will not receive a receipt";
    }

    private string chkRecurring_CheckedChanged(object sender, EventArgs e)
    {
        if (chkRecurring.Checked)
        {
            return "You will be charged monthly";
        }
        else
            return "This is a one time payment";
    }

And here’s what the form looks like:

What am I doing wrong here? I apologize, but I’m still pretty new to C# and VS 2010.

Thanks,
Ray

Answer 1

You can’t return things from an event handler. Do you mean to show a message box instead? Or give feedback through a label? It would be something like:

private string void rdoMastercard_CheckedChanged(object sender, EventArgs e)
{
    if (rdoMastercard.Checked)
        return MessageBox.Show("You have selected Mastercard");
    else
        return MessageBox.Show("You have selected Visa");
}

and the same for your other examples. This example uses a message box but you can set a Label’s text or whatever.

The reason? How do you expect C# to know what you want to do when you’re returning something from an event handler? An event handler handles events, nothing more.

Edit: So for what you want to do, it would be something like:

private void btnConfirmChoices_Click(object sender, EventArgs e) {
    string str = string.Empty;

    if(rdoMastercard.Checked)
        str += "You have selected Mastercard\n";
    else
        str += "You have selected Visa\n";

    if (chkReceipt.Checked)
        str += "You will receive a receipt\n";
    else
        str += "You will not receive a receipt\n";

    if (chkRecurring.Checked)
        str += "You will be charged monthly";
    else
        str += "This is a one time payment";

    MessageBox.Show(str);
}