Winform: Validating in non-Form class

Song Lee

Hello,
my goal is to write a Validate class, and call it over to Form1.cs.
I've seen ways to validate user input through Form1.cs, but never on the normal class.
Will it be possible to validate textBox or comboBox input?
Thank you.

5 Replies

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Vulpes11y ago
Accepted answer
For the type of validation you're doing, you'll need to replace this method:

public static bool ValidateString(Control c, out int i)
{
return int.TryParse(c.Text, out i);
}

with this:

public static bool ValidateString(string s)
{
return s.Length > 0 && s[0] != ' ';
}
Song Lee11y ago
Thank you very much everyone :)
Song Lee11y ago
Gahh;; I'm a bit confused atm >.<

////////////////////////////////////////////////////////////////////////////////////////////////////
Form cs.

private bool ValidateContact(ContactFiles.Contact contact)
{
if (!InputUtility.ValidateString(contact.FirstName))
{
MessageBox.Show("You must enter a first name with atleast one character (not a blank)", "Error!", MessageBoxButtons.OK, MessageBoxIcon.Error);

firstText.Focus();
firstText.Text = " ";
firstText.SelectAll();
return false;
}
else if (!InputUtility.ValidateString(contact.LastName))
{
MessageBox.Show("You must enter a last name with atleast one character (not a blank)", "Error!", MessageBoxButtons.OK, MessageBoxIcon.Error);

secondText.Focus();
secondText.Text = " ";
secondText.SelectAll();
return false;
}
return true;
}

/////////////////////////////////////////////////////////////////////////////////////////////////////////
non-form class:

using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms; //Added

namespace Assignment_6_attempt_1
{
static class InputUtility
{
public static bool ValidateString(Control c, out int i)
{
return int.TryParse(c.Text, out i);
}

}

//I'm not too sure what to put in this method D:
//Getting: error: No overload for method "validateString" takes 1 arguments
Vulpes11y ago
Well, it's certainly possible (though unusual) to validate form input in a separate non-form class.

This may give you some pointers as to how you could do it:

/* Validation.cs */

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows.Forms; // add this

namespace WindowsFormsApplication1
{
// validate controls which have a Text property

static class Validation
{
public static bool IsInteger(Control c, out int i)
{
return int.TryParse(c.Text, out i);
}

// overload to deal with integers in a range
public static bool IsInteger(Control c, int min, int max, out int i)
{
return int.TryParse(c.Text, out i) && i >= min && i <= max;
}

public static bool IsDouble(Control c, out double d)
{
return double.TryParse(c.Text, out d);
}

// overload to deal with doubles in a range
public static bool IsDouble(Control c, double min, double max, out double d)
{
return double.TryParse(c.Text, out d) && d >= min && d <= max;
}
}
}

/* Form1.cs */

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace WindowsFormsApplication1
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}

private void textBox1_Leave(object sender, EventArgs e)
{
int i;
bool isValid = Validation.IsInteger(textBox1, 1, 10, out i);
if (!isValid)
{
MessageBox.Show("Must be an integer between 1 and 10. Please amend.", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
textBox1.Focus();
return;
}
else
{
MessageBox.Show("The integer " + i + " was entered", "Valid input", MessageBoxButtons.OK);
}
}

private void textBox2_Leave(object sender, EventArgs e)
{
double d;
bool isValid = Validation.IsDouble(textBox2, out d);
if (!isValid)
{
MessageBox.Show("Must be numeric. Please amend.", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
textBox2.Focus();
return;
}
else
{
MessageBox.Show("The double " + d + " was entered", "Valid input", MessageBoxButtons.OK);
}
}
}
Selva Ganapathy11y ago

Hi Song,
Did you try to pass the String return form textbox of ComboBox my textbox.Text or coboBox.Text?
Or why cant you use TextValidation event of the TextBox control to make use of your own validation class here?
Regards,
Selva Ganapathy K