C# – Masked TextBox Validating Text Error

cwinforms

I'm having some trouble with date variables extracted from a masked textbox on a WinForms app.
The code which attempts to read the user input date is as follows:

DateTime datExpDate = new DateTime();
datExpDate = (DateTime)txtExpDate.ValidateText();

But I get a NullReferenceException error, even when the masked text box is deinately not Null.

The properties on the masked text box include:

Mask: 00/00/0000
Validating Type: DateTime
TextMaskFormat: IncludeLiterals

This is exactly as I have used masked textboxes on previous apps and it worked then, so why not now?

Can anyone spot what I am doin wrong please?

Best Answer

Here is the solution from MSDN:

    private void Form1_Load(object sender, EventArgs e)
{
    maskedTextBox1.Mask = "00/00/0000";
    maskedTextBox1.ValidatingType = typeof(System.DateTime);
    maskedTextBox1.TypeValidationCompleted += new TypeValidationEventHandler(maskedTextBox1_TypeValidationCompleted);
    maskedTextBox1.KeyDown += new KeyEventHandler(maskedTextBox1_KeyDown);

    toolTip1.IsBalloon = true;
}

void maskedTextBox1_TypeValidationCompleted(object sender, TypeValidationEventArgs e)
{
    if (!e.IsValidInput)
    {
        toolTip1.ToolTipTitle = "Invalid Date";
        toolTip1.Show("The data you supplied must be a valid date in the format mm/dd/yyyy.", maskedTextBox1, 0, -20, 5000);
    }
    else
    {
        //Now that the type has passed basic type validation, enforce more specific type rules.
        DateTime userDate = (DateTime)e.ReturnValue;
        if (userDate < DateTime.Now)
        {
            toolTip1.ToolTipTitle = "Invalid Date";
            toolTip1.Show("The date in this field must be greater than today's date.", maskedTextBox1, 0, -20, 5000);
            e.Cancel = true;
        }
    }
}

// Hide the tooltip if the user starts typing again before the five-second display limit on the tooltip expires.

void maskedTextBox1_KeyDown(object sender, KeyEventArgs e)
{
    toolTip1.Hide(maskedTextBox1);
}

LINK: http://msdn.microsoft.com/en-us/library/system.windows.forms.maskedtextbox.validatingtype.aspx

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# – Bind nullable DateTime to MaskedTextBox

I figured out it didn't have to do with the validation. It was when the date was being parsed back to the datetime.

This may not be the most elegant way to do this, but it does work. If anyone knows a better way, please let me know.

I have this code now.

public static void FormatDate(MaskedTextBox c) {
    c.DataBindings[0].Format += new ConvertEventHandler(Date_Format);
    c.DataBindings[0].Parse += new ConvertEventHandler(Date_Parse);
}

private static void Date_Format(object sender, ConvertEventArgs e) {
    if (e.Value == null)
        e.Value = "";
    else
        e.Value = ((DateTime)e.Value).ToString("MM/dd/yyyy");
}

static void Date_Parse(object sender, ConvertEventArgs e) {
    if (e.Value.ToString() == "  /  /")
        e.Value = null;
}

Best Answer

Related Solutions

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

C# – Bind nullable DateTime to MaskedTextBox

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