Custom Libraries


The Visual Basic Library

The Windows controls featured in the .NET Framework are highly varied and provide most of the necessary regular functionality a normal application would need. They do this through various properties and their different methods. Here is an example of a form with a few controls:

To enhance their functionality and speed up application development, Visual Basic offers a very extended library of functions to cover different issues including mathematics, finance, date, time, and commerce, etc.

To use a Visual Basic function in your application, you can add its reference to your project. To add a reference to the Visual Basic library, on the main menu, you can click Project -> project-X Properties... In the Properties Pages, you can Add New Reference... This would display the Add Reference dialog box. In the .NET property page and in the list under the Component Name header, you can click Microsoft.VisualBasic

Add Reference

After making the selection, you can click OK. Also, in the Property Pages, you can click OK

Alternatively, you can manually add a reference to the Microsoft.VisualBasic.dll assembly in your file:

#using <Microsoft.VisualBasic.dll>

Then, you must locate and identify the particular function you want to use. Here are examples

System::Void btnCalculate_Click(System::Object^  sender, System::EventArgs^  e)
    double base, height, area;

    // Use Visual Basic's IsNumeric() function to validate the value of the text box
    if( !Microsoft::VisualBasic::Information::IsNumeric(this->txtBase->Text) )
	 base = 0.00;
    else // If the user entered a number, convert it to a valid double number
	 base = Microsoft::VisualBasic::Conversion::Val(this->txtBase->Text);

    if( !Microsoft::VisualBasic::Information::IsNumeric(this->txtHeight->Text) )
	 height = 0.00;
	 height = Microsoft::VisualBasic::Conversion::Val(this->txtHeight->Text);

    // Perform the corresponding operation
    area = base * height / 2;

    // Display the result in the Result text box
    this->txtArea->Text = area.ToString();

Creation of a Custom Library

The .NET Framework as a library is very huge. It is even more enhanced when combined with Win32. But no matter how large a library is, it cannot possibly meet every one's need. For this reason, sometimes you will need to create an additional library of functions and/or classes you can use in different programs. Fortunately, it is very easy to create a library. The most difficult is probably about what you will decide to put in the library.

You can start by creating a project (on the main menu, File -> New -> Project...). In the Project Types list, you would select Class Library and give it a name. Here is an example:

New Project

And click OK. In the Solution Explorer, you would open the header file and type the code for the library. Here is an example:

// ItemDescription.h

#pragma once

using namespace System;

namespace ItemDescription
    public ref class CPartDescription
        String ^ number;
        String ^ discr;
        double  uprice;

	    this->number = L"";
	    this->discr  = L"";
	    this->uprice = 0.00;

	CPartDescription(String ^ nbr, String ^ name, double price)
	    this->number = nbr;
	    this->discr  = name;
	    this->uprice = price;

        property String ^ ItemNumber
	    String ^ get() { return number; }
	    void set(String ^ nbr) { number = nbr; }

        property String ^ ItemName
	    String ^ get() { return discr; }
            void set(String ^ desc) { discr = desc; }

	property double UnitPrice
	    double get() { return uprice; }

            void set(double price) { uprice = price; }

	virtual String ^ ToString() override
		return String::Concat(this->ItemNumber,
			                  L" ",
					  L" ",

To actually create the library, on the main menu, you would click Build -> Build project-X.


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