VS 2010 - Converting String To Datetime

I have a maskededit extender

Code:

TargetControlID="dateTextBox"
Mask="99/99/9999 99:99"
MessageValidatorTip="true"
OnFocusCssClass="MaskedEditFocus"
OnInvalidCssClass="MaskedEditError"
MaskType="DateTime"

[Code] ....

So the input format looks like this 12/23/2012 12:12 AM

And I would like to convert this as datetime so i tried to do

Code:
Dim ab As DateTime
ab = DateTime.Parse(dateTextBox.Text)

But it's showing me an error

Code:
at System.DateTimeParse.Parse(String s, DateTimeFormatInfo dtfi, DateTimeStyles styles)
at System.DateTime.Parse(String s)
at admin_trackadd.saveButton_Click(Object sender, EventArgs e)