WinForms and child forms - How to consolidate redundant "utility" code?

I searched and Googled first, thinking surely someone must have asked this before, but I sure can't find a good description of this problem.

I have six or eight similar C# .NET 2.0 WinForms applications built with the fairly common model of a main application window with several GUI data fields plus several modal dialogs for further data collection. Many of the data fields (especially TextBoxes) have identical data validation routines. I'm writing the same xxx_Validating() routines over and over, which in the simplest case only capitalize the first character of the entered text (if any) and redisplay the result. I have another one for ZIP Code fields that takes the first 3 digits of a 5-digit US postal ZIP Code and returns the corresponding State, using a 1000-member string array. Simple stuff. There are a few others; here's an example:

public void CapFirstCharTextBox_Validating(object sender, CancelEventArgs e)
{
    string strValue = ((TextBox)sender).Text.Trim();
    if (strValue.Length >= 1) {
        if (char.IsLower(strValue[0])) {
            strValue = strValue.Substring(0, 1).ToUpper() + strValue.Substring(1);
            ((TextBox)sender).Text = strValue;     // fires (whatever sender)_TextChanged()
        }
    }
}

Again this is part o开发者_JAVA百科f a half-dozen or so such "utility" routines. I've only got one set of these per dialog box class, and all the various TextBoxes in that dialog which need this have their Validating event pointing to the same method. So it's not like I've got 20 of these in a given source file (one for each TextBox) or anything; there's only one for the whole dialog class.

Problem is, the whole set of these exists in every source file where I need them. That's one set for the main window and more for each pop-up dialog box -- and that's too many. I understand modal dialog box classes can't communicate with each other, and making all this stuff global is elusive at best and a big "no-no" at worst.

I have successfully tried passing a reference to "FormMain" (where one copy of these routines exist) to the various dialog constructors, and then calling these validation routines with that from their own validation handlers. It works but feels awfully clunky and certainly not like the best approach.

So, how would I (or would I want to) rearrange the project and organize the code better to have only a single instance of these kinds of things? How would I wire up a global "utility" class of such methods such that I can get to it from the main form's code and from that of a bunch of pop-up modal dialog boxes as well?

I'd like to maintain just one executable with no additional .DLLs if possible (these are all one-project-per-solution, by the way), and if practical I'd like to further be able to share that common code across multiple solutions.

I think the answer will include writing new assemblies, using different namespaces (currently all my code in a given project is contained in the same namespace), and maybe separating this stuff out into its own project in the same solution file.

Is it possible?

You can share code across solutions by keeping the code in one place and adding a link to the file in each solution.

To add a link: right click the project (or folder) you want to add the code to, then select "Add existing item", browse for the file, when found click the down arrow on the button and pick Link to.

This way the projects that link to the file will share the same code.

BTW: take care when using a source control system that doesn't know how to handle these links.