Update Label Without Button

Is there a way to make a label automatically update itself so that I don't have to use a button to send out the command. What I have setup is a subtotal textbox, discount textbox, tax label, shipping textbox, and total label. So, when people fill in the subtotal, discount, and shipping, I want the tax label to be calculated, but only if previously a 开发者_Python百科certain state was selected in another part of the form. So then, with all those filled in, I want the total label to be filled in. All of these I know I can do with a button, but I was wondering if there is a way to automate it using C# in Visual Studio.

Thanks.

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I use the TextChanged Event to update such values between pairs of textboxes. Here are some extracts of my code:

private void onLongitudeTextChanged(object sender, EventArgs e) {
           updateDistanceAndBearing();
        }

updateDistanceAndBearing does some error checking - this can be a good idea if the user can put invalid values in and then updates the Text property of the other TextBoxes I have text boxes but update the label.Text property instead.

It gets more messy (at least I found it so) if you have numeric updowns to get values

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You can call a method to update the label in the change events for the controls.

For more detail, please supply more detail.

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this is off the top of my head but should get you pretty close...

private void taxChanged(object sender, EventArgs e)
        {
             updateTax();
        }


private void updateTax()
        {
            // the rest of your logic, checking state, etc. 
            // 
            this.Tax.Text = aValueCalculatedInYourLogicAbove;
            updateTotal()
        }

private void updateTotal()
        {
            // sum up whatever fields need to be summed 
            // 
            this.Tax.Text = aTotalValueCalculatedAbove;
        }