A regular expression can be a single character, or a more complicated pattern.
Regular expressions can be used to perform all types of text search and text replace operations.
The first issue is that our properties are appearing at the bottom of the Properties list under the Misc category, which is the default behavior if you do not set a specific category.
In Java Script, regular expressions are often used with the two string methods: search() and replace().
The search() method uses an expression to search for a match, and returns the position of the match.
In this case I don't want to use a User Control, since I am inheriting from an existing control, so I am going to delete that file and just add a new class file.
With just that little bit of code I have already created my own version of the Text Box by inheriting from the existing control.
NET: Introduction Sample 1a: Adding Regular Expression Validation to the Text Box Control A Short Discussion on Regular Expressions What Do I Need to Build?
Sample 1b: Adding Regular Expression Validation an Alternative Way Summary Two samples are covered in this article: creating a custom Text Box that performs regular expression validation, and creating an extender provider that uses a different method to perform the same regular expression validation.
NET class: To use this new property and check the validity of the Text Box contents, use the System. With this code, a regular expression designed to find five-digit zip codes would match the first five digits in a string such as "23434fred" despite the extra text added on at the end. Length Then Return True Else Return False End If Catch 'some form of error in parsing the pattern Return False End Try End Function Windows Forms controls provide a variety of methods and events dealing with validation already, so it seems appropriate to fit my new Regular Expression check into that existing model by checking the Text Box contents in the On Validating method. On Validating(e) End Sub Put all of this code together and you have a complete control that you can try out.
What we actually want to test is whether the string and the expression are exactly matched. This method will be called whenever the control loses focus and the control's Causes Validation property is equal to True. Build the control project, and then go into the test project (a Windows Application that has been added to the same solution), add a reference to your Reg Ex Text Box project and customize the toolbox to show your new control.
For this control, there are two properties: Valid and Regular Expression. Category attribute is what you will use to specify the appropriate category, but note that it just takes a string as an argument, so make sure you spell the category name correctly: Figure 1.