C# – Form Validation using ErrorProvider and Validating Events

cerror handlingerrorprovidervalidationwinforms

I'm fairly new to using validation. I have a C# winform project that I want to validate a form before closing. However, I only want this validation to occur when I click a button. So I have an event that fires for that like so:

if (!this.ValidateChildren())
{
   MessageBox.Show("Validation failed");
}
else
{
   MessageBox.Show("Validation passed with flying colours. :)");
   this.Close();
}

I only want to close the form if the validation is successful. Easy enough. However, I don't want to have the validation run when the textboxes lose focus, only when the whole form is being validated.

Each control that I want to be validated, I have registered with the "validating" event. They use "e.Cancel = true;" to cancel the validation. I have been using the ErrorProvider class to support this visually.

So basic question is, what is the best approach to validate a specific set of controls only when I want to and not when focus is lost from the control?

EDIT: presently as a work around, I have a method that toggles the "CausesValidation" property on and off. I default everything to not CauseValidation, enables them all before I use the event for validating the whole form, and disables them all after again.

I really don't see this as an ideal approach. Are there any more 'elegant' solutions out there?

Best Answer

I think this is the best way to go with validation using Error Provider Component

(Or) Try this

http://www.c-sharpcorner.com/uploadfile/john_charles/validating-data-entry-in-windows-forms-application/

Related Solutions

C# – Cross-thread operation not valid: Control accessed from a thread other than the thread it was created on

As per Prerak K's update comment (since deleted):

I guess I have not presented the question properly.

Situation is this: I want to load data into a global variable based on the value of a control. I don't want to change the value of a control from the child thread. I'm not going to do it ever from a child thread.

So only accessing the value so that corresponding data can be fetched from the database.

The solution you want then should look like:

UserContrl1_LOadDataMethod()
{
    string name = "";
    if(textbox1.InvokeRequired)
    {
        textbox1.Invoke(new MethodInvoker(delegate { name = textbox1.text; }));
    }
    if(name == "MyName")
    {
        // do whatever
    }
}

Do your serious processing in the separate thread before you attempt to switch back to the control's thread. For example:

UserContrl1_LOadDataMethod()
{
    if(textbox1.text=="MyName") //<<======Now it wont give exception**
    {
        //Load data correspondin to "MyName"
        //Populate a globale variable List<string> which will be
        //bound to grid at some later stage
        if(InvokeRequired)
        {
            // after we've done all the processing, 
            this.Invoke(new MethodInvoker(delegate {
                // load the control with the appropriate data
            }));
            return;
        }
    }
}

C# – How to make a textbox that only accepts numbers

Two options:

Use a NumericUpDown instead. NumericUpDown does the filtering for you, which is nice. Of course it also gives your users the ability to hit the up and down arrows on the keyboard to increment and decrement the current value.

Handle the appropriate keyboard events to prevent anything but numeric input. I've had success with this two event handlers on a standard TextBox:

private void textBox1_KeyPress(object sender, KeyPressEventArgs e)
{
    if (!char.IsControl(e.KeyChar) && !char.IsDigit(e.KeyChar) &&
        (e.KeyChar != '.'))
    {
            e.Handled = true;
    }

    // only allow one decimal point
    if ((e.KeyChar == '.') && ((sender as TextBox).Text.IndexOf('.') > -1))
    {
        e.Handled = true;
    }
}

You can remove the check for '.' (and the subsequent check for more than one '.') if your TextBox shouldn't allow decimal places. You could also add a check for '-' if your TextBox should allow negative values.

If you want to limit the user for number of digit, use: textBox1.MaxLength = 2; // this will allow the user to enter only 2 digits

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