interactively validating user input in the .net textbox

Question

how does one interactively prevent the user from inputting invalid characters in input controls of vb .net..... it seems the the keypress event of the .net input controls is read only and therefore cannot be assigned a zero(0) or null("") value unlike in vb6 where one can set the value of the keyascii parameter of the keypress event to 0 to prevent characters typed from being shown is there some other way to do the above in vb .net

hhill · Answer

Here is a simple method sample in C# /// /// validateNameEntry - Used to validate that the name the user inputed into the textBoxName control /// is between 1 and 50 characters in length and contains only alphnumerical or whitespace characters in the string. /// /// private bool validateNameEntry() { if(this.textBoxName.Text.Length > 0 && this.textBoxName.Text.Length < 50) { for(int loop=0; loop < this.textBoxName.Text.Length; loop++) { bool validLetter = (char.IsLetter(this.textBoxName.Text loop)); bool validNumber = (char.IsNumber(this.textBoxName.Text loop)); bool validWhitespace = (char.IsWhiteSpace(this.textBoxName.Text loop)); if(validLetter == false && validNumber == false && validWhitespace == false) { return(false); } } return(true); } else return(false); }

joy.simpson · Answer

Also available are the following: IsDigit IsLetter IsLetterOrDigit IsNumber IsSymbol IsPunctuation IsLower IsUpper Add = False or leave it out (same as = True) and try combining the above as needed.

joy.simpson · Answer

Sure. Here's an example for entering only numbers: Private Sub TextBox1_KeyPress(ByVal sender As Object ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles TextBox1.KeyPress If e.KeyChar Chr(8) Then 'this allows user to delete with the backspace key If Not Char.IsDigit(e.KeyChar) Then e.Handled = True End If End If End Sub and here's an example for entering only letters: Private Sub TextBox2_KeyPress(ByVal sender As Object ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles TextBox2.KeyPress If Not Char.IsNumber(e.KeyChar) = False Then e.Handled = True End If End Sub