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How to cancel Button click action when required fields are empty?

I have two procedures in a form. One of them checks null fields and the second one inserts a record.

private void CheckNullValues()
{
if (textBox1.Text == "") {
MessageBox.Show("Field [Email] can not be empty","Information",MessageBoxButtons.OK, MessageBoxIcon.Information);
textBox1.Focus();
return();
}
}

private void buttonAdd_Click(object sender, EventArgs e)
{
CheckNullValues();
MessageBox.Show("Insert record");
}


How can I stop executing the action in CheckNullValues procedure if the textBox1 is empty and not let it show MessageBox.Show("Insert record")?

CheckNullValues

MessageBox.Show("Insert record")

CheckNullValues

bool

private bool ValidInputs() { // ... }

if(!ValidInputs()) return;

3 Answers
3

You need to change the type of your CheckNullValues method to bool in order for it to return a true or false value depending on whether the TextBox(es) is/are empty or not.

CheckNullValues

bool

You might also want to change its name to something that reflects the returned value. I usually use something like this:

private bool ValidInputs()
{
if (string.IsNullOrEmpty(textBox1.Text))
{
MessageBox.Show("Field [Email] can not be empty","Information",
MessageBoxButtons.OK, MessageBoxIcon.Information);
textBox1.Focus();
return false;
}
if (string.IsNullOrEmpty(textBox2.Text))
{
// ...
return false;
}

return true;
}


Then in your button click event, you can easily do something like:

if (!ValidInputs()) return;


Moreover, to avoid repeating code in the ValidInputs() method, you can move the logic for validating the TextBox contents to separate method:

ValidInputs()

public bool TextBoxEmpty(TextBox txtBox, string displayMsg)
{
if (string.IsNullOrEmpty(txtBox.Text))
{
MessageBox.Show(displayMsg, "Required field",
MessageBoxButtons.OK, MessageBoxIcon.Information);
txtBox.Focus();
return true;
}

return false;
}


That way, your ValidInputs() method becomes:

ValidInputs()

private bool ValidInputs()
{
if (TextBoxEmpty(textBox1, "Field [Email] can not be empty")) return false;
if (TextBoxEmpty(textBox2, "Some other message")) return false;
// ...

return true;
}


If the function checking if something is null is set to return true or false you can then use an if statement in your click event.

if (!checkForNulls()) {
MessageBox.Show("Insert record");
}


Please modify your code as below:
private bool CheckNullValues()
{

if (textBox1.Text == "")
{
MessageBox.Show("Field [Email] can not be empty", "Information", MessageBoxButtons.OK, MessageBoxIcon.Information);
textBox1.Focus();
return false;
}
else
{
return true;
}
}

private void buttonAdd_Click(object sender, EventArgs e)
{
if (CheckNullValues())
{
MessageBox.Show("Insert record");
}
}


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