Multiple textbox validation

Question

I'm beginner studying for c#. If I have 2 textbox, can I validate 2 textbox in 1 if statement?

For example:

{
    string emptytextbox
    if (textBox1.Text == "" || textBox2.Text == "" || textBox3.text == "")
    {
        //if textbox2 is empty, then messagebox will show
        emptytextbox = textBox2.text;
        mbox(emptytextbox + " must be filled");

        //messagebox will show "textBox2 must be filled"
        //but if textbox1&2 has ben filled, but textbox3 empty,then messagebox will show "textbox3 must be filled"
    }
}

Can I do this?

It depends on your requirement. If you want to performance some action when both text boxes are empty then you can have one if-statement, otherwise you need multiple if-condition either nested or separate. — Hassan Nisar
– Hassan Nisar, Commented Jun 14, 2014 at 17:03
There is better way to achieve this functionality. Are you working on windows form application. — Hassan Nisar
– Hassan Nisar, Commented Jun 14, 2014 at 17:06

chfumero · Accepted Answer · 2014-06-14 17:32:57Z

1

One condition return a boolean value, there is no way to know witch one is the empty textbox. When you write an or expression the condition evaluate true if any of the components evaluate true. In this case when you go inside the condition the fact is that at least one of the conditions is true (by condition I mean textBox1.Text == "").

On this case the best way to perform the validation must be something like this:

void VerificationFunction()
    {
        CheckTextBox(textbox1);
        CheckTextBox(textbox2);
        CheckTextBox(textbox3);
    }

void CheckTextBox(TextBox tb)
    {
        if (string.IsNullOrEmpty(tb.Text))
        {
            MessageBox.Show(tb.Name + "must be filled");
        }
    }

edited Jun 14, 2014 at 17:32

answered Jun 14, 2014 at 17:13

chfumero

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Comments

Hassan Nisar · Accepted Answer · 2014-06-14 17:34:22Z

can I validate 2 textbox in 1 "if" statement?

NO. Because you have to check every textBox and inform user about specific textBox which is left empty.

For all three textbox you can do something like that:

if (textBox1.Text == "")       
     MessageBox.Show("textBox1 must be filled");
if (textBox2.Text == "")       
     MessageBox.Show("textBox2 must be filled");
if (textBox3.Text == "")       
     MessageBox.Show("textBox3 must be filled");

It is good practice to have one method for the purpose.

Here is method which can be used to check each TextBox on the form. If there is any empty TextBox it will show message to user that textbox must be filled. Good practice is to inform user once.

private void ValidateTextBoxes()
    {
        foreach (Control c in this.Controls)
        {
            if (c is TextBox)
            {
                if (string.IsNullOrEmpty(c.Text))
                {
                    MessageBox.Show(c.Name + " must be filled");
                    break;
                }

            }
        }
    }

Usman Ali · Accepted Answer · 2017-04-27 06:29:06Z

0

Best way is to do it separately

if (String.IsNullOrEmpty(textBox1.Text))
{
     textBox1.BorderBrush = System.Windows.Media.Brushes.Red;
}
if (String.IsNullOrEmpty(textBox2.Text))
{
     textBox2.BorderBrush = System.Windows.Media.Brushes.Red;
}

answered Apr 27, 2017 at 6:29

Usman Ali

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