C＃事件点击包含多个方法

Question

I am trying to nest methods, or place methods within other methods. Using C# and Microsoft Visual Studio for the first time and my dilemma is this. I have created form with an event click button to validate user input, which is fine in itself, but I need to validate more than one input when the button is clicked. In the Calculate button's click event handler, perform input validation on the three text boxes (the three that the user will use for data entry). For code efficiency I want to use separate methods to achieve this. I have tried writing more methods directly within the event handler, but no matter how I start the method public, private, static, void, main etc I always get errors. Any assistance/advice would be greatly appreciated.

private void btnCalculate_Click(object sender, EventArgs e)      
        {                     
            int txtLength = 0;
            if ((txtLength < 5) & (txtLength > 50))
                MessageBox.Show("Length measurement is invalid" + "\r\n" + "Please enter a value between 5 and 50", "Data Invalid"); 


            int txtWidth = 0;         
            if ((txtWidth < 2) & (txtLength > 20))
                MessageBox.Show("Width measurement is invalid" + "\r\n" + "Please enter a value between 2 and 20");


            int txtAvgDepth = 0;
            if ((txtAvgDepth < 2) & (txtAvgDepth > 4))
                MessageBox.Show("Width measurement is invalid" + "\r\n" + "Please enter a value between 2 and 20");*/
        }

Changed code in method along with the error messages it throws. The original code had no syntax errors.

Problem solved. Thank you all very much for your help :)

Answer 1

Just add them to the class:

private void CalculateButton_Click(object sender, EventArgs e)      
{
    ValidateLength();
    ValidateWidth();
    ValidateDepth();
}

private void ValidateLength() 
{
    int txtLength = LengthTextBox.Value;
    if ((txtLength < 5) & (txtLength > 50))
        MessageBox.Show("Length measurement is invalid" + "\r\n" + "Please enter a value between 5 and 50", "Data Invalid"); 
}

private void ValidateWidth()
{
    int txtWidth = WidthTextBox.Value;         
    if ((txtWidth < 2) & (txtLength > 20))
        MessageBox.Show("Width measurement is invalid" + "\r\n" + "Please enter a value between 2 and 20");
}

private void ValidateDepth()
{
   int txtAvgDepth = DepthTextBox.Value;
   if ((txtAvgDepth < 2) & (txtAvgDepth > 4))
            MessageBox.Show("Depth measurement is invalid" + "\r\n" + "Please enter a value between 2 and 4");*/
}

I guess you're trying to tidy this up and have a single validation routine:

private void CalculateButton_Click(object sender, EventArgs e)      
{
    ValidateRange(LengthTextBox.Value, 5, 50, "Length");
    ValidateRange(WidthTextBox.Value, 2, 20, "Width");
    ValidateRange(DepthTextBox.Value, 2, 4, "Depth");
}

private void ValidateRange(int value, int min, int max, string msg) 
{
    if (value < min || value > max)
        MessageBox.Show(
            string.Format("{0} measurement is invalid\r\nPlease enter a value between {1} and {2}", msg, min, max), 
            "Data Invalid"); 
}

Answer 2

Click Handlers are known as delegates, they subscribe to events in a one-event, many subscribers fashion. What you are trying to achieve is completely possible but not from the IDE GUI, as it is designed to manage a single subscription. You could instead subscribe to the event from code like this

btnCalculate.Click += ClickHandler1;
btnCalculate.Click += ClickHandler2;
btnCalculate.Click += ClickHandler3;

Even though it's possible, i'd strongly advise against it as it seems over-engineered and it's not really how the platform was thought out to be used. It shouldn't have any bad side effects as the .Net event/delegate system is ready to handle this use case but the maintainability suffers in the process.

I'd rather go with an orchestrator method. Subscribe once and call each validation method from there.

More reading material:

• https://msdn.microsoft.com/en-us/library/17sde2xt%28v=vs.90%29.aspx
• https://msdn.microsoft.com/en-us/library/bb534960(v=vs.110).aspx
• https://msdn.microsoft.com/en-us/library/018hxwa8(v=vs.110).aspx