C# – create a textbox that accepts only numeric values. Problem with designer mode

cwinforms

i have a form that has some six – seven text boxes. few text boxes needs to accept only numeric chars i.e from 0-9, a decimal poing and + or –

i handled the textbox key press event

private void textBox1_KeyPress(object sender, KeyPressEventArgs e)
{
if (!char.IsControl(e.KeyChar)
&& !char.IsDigit(e.KeyChar)
&& e.KeyChar != '.')
{
e.Handled = true;
}

}

Now i have to write the same code for all the textboxes which i felt is redudant.
I created a new class MyTextBox derived from TextBox and added the above code into it.

In the designer mode i drag and drop the textbox control .. go to the Designer.cs file and change the line to

private MyTextbox m_txtName = new MytextBox();

Now the problem is that if i add a new button or any control to teh form the designer.cs file is changed/updated… and the aboe line is changed to the normal TextBox and i got to go replace this everytime … can i avoid this ?

Note: I do not want to use MasktextBox or numericKeydown control.

Best Answer

An excellent example you will find here.

As about designer. When you will rebuild your project, you will(should) see your textBox as a custom component in the Toolbox. Drag and drop that component instead of your ancient textBoxes.

If not, you need to find all the references of your MyTextBox1 because you need to change it in at least 2 places: declaration and creation(MyTextBox mtb; and mtb = new MyTextBox();)

Related Solutions

C# – How to make a textbox that only accepts numbers

Two options:

Use a NumericUpDown instead. NumericUpDown does the filtering for you, which is nice. Of course it also gives your users the ability to hit the up and down arrows on the keyboard to increment and decrement the current value.

Handle the appropriate keyboard events to prevent anything but numeric input. I've had success with this two event handlers on a standard TextBox:

private void textBox1_KeyPress(object sender, KeyPressEventArgs e)
{
    if (!char.IsControl(e.KeyChar) && !char.IsDigit(e.KeyChar) &&
        (e.KeyChar != '.'))
    {
            e.Handled = true;
    }

    // only allow one decimal point
    if ((e.KeyChar == '.') && ((sender as TextBox).Text.IndexOf('.') > -1))
    {
        e.Handled = true;
    }
}

You can remove the check for '.' (and the subsequent check for more than one '.') if your TextBox shouldn't allow decimal places. You could also add a check for '-' if your TextBox should allow negative values.

If you want to limit the user for number of digit, use: textBox1.MaxLength = 2; // this will allow the user to enter only 2 digits

C# – How to get a TextBox to only accept numeric input in WPF

Add a preview text input event. Like so: <TextBox PreviewTextInput="PreviewTextInput" />.

Then inside that set the e.Handled if the text isn't allowed. e.Handled = !IsTextAllowed(e.Text);

I use a simple regex in IsTextAllowed method to see if I should allow what they've typed. In my case I only want to allow numbers, dots and dashes.

private static readonly Regex _regex = new Regex("[^0-9.-]+"); //regex that matches disallowed text
private static bool IsTextAllowed(string text)
{
    return !_regex.IsMatch(text);
}

If you want to prevent pasting of incorrect data hook up the DataObject.Pasting event DataObject.Pasting="TextBoxPasting" as shown here (code excerpted):

// Use the DataObject.Pasting Handler 
private void TextBoxPasting(object sender, DataObjectPastingEventArgs e)
{
    if (e.DataObject.GetDataPresent(typeof(String)))
    {
        String text = (String)e.DataObject.GetData(typeof(String));
        if (!IsTextAllowed(text))
        {
            e.CancelCommand();
        }
    }
    else
    {
        e.CancelCommand();
    }
}

Best Answer

Related Solutions

C# – How to make a textbox that only accepts numbers

C# – How to get a TextBox to only accept numeric input in WPF

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