Validation of textboxes

Question

Hello How can i validate a textbox? For example if user enters 1 in a date textfield should get an error message and postpone the action(insertedit). The same goes with numeric textfields. Thank you in advance.

Nilanka Dharmadasa · Answer

DateTime result = new DateTime (); if (! DateTime .TryParse(textBox1.Text out result)) { MessageBox .Show( error ); }

Dealy · Answer

Thank you all for your help.

jinge · Answer

As I told you in your previous post you can use DateTime.TryParse method. You can pass culture info to the method which make sure the application can parse time correctly based on different cultures.

Kirtan Patel · Answer

// Check if Value is Numeric //Note :- You can also Do following using RegEx :-) Better to Use RegEx for TextBox Validations // Because we can validate whatever format we want by building custom expressions private void textBox1_KeyPress( object sender KeyPressEventArgs e) { if ( Char .IsDigit(e.KeyChar) == true || e.KeyChar == ( char ) Keys .Back) { e.Handled = false ; } else { e.Handled = true ; } } Use Masked TextBox For Getting Date From the User //Date validation ( mm/dd/yyyy) using RegEx private void maskedTextBox1_Leave( object sender EventArgs e) { Regex re = new Regex ( (0[1-9]|1[012])[- /.](0[1-9]|[12][0-9]|3[01])[- /.](19|20)[0-9]{2} ); if (re.IsMatch(maskedTextBox1.Text.Trim()) == false ) { MessageBox .Show( Date Not valid !! ); } else { //If Valid //statements } } if you want to check Date Valid in dd/mm/yyyy then use below regex syntax (0[1-9]|[12][0-9]|3[01])[- /.](0[1-9]|1[012])[- /.](19|20)[0-9]{2} //How to Build your own Numeric Validator if (! string .IsNullOrEmpty(textBox1.Text.Trim())) { char [] Digits = textBox1.Text.ToCharArray(); bool flag = true ; foreach ( char c in Digits) { if (! char .IsNumber(c)) { flag = false ; break ; } } if (flag == false ) { MessageBox .Show( Not Valid Number is entered  ); } } else { MessageBox .Show( No value is Entered! ); }

Nilanka Dharmadasa · Answer

Use DateTime.TryParse method.