Control Identification

Introduction

As you should know from your learning C#, in order to use a variable in your application, you must declare a variable for it and, when declaring a variable, you must give it a name. This rule also applies to Windows controls you will use in your application. Based on this, and as seen in the previous lesson, you can programmatically create a control by declaring a variable for and give that variable a name.

To create a control, the primary piece of information you must provide is its name. This allows you and the compiler to know what control you are referring to when the program is running. Specifying the name of a control may depend on the technique you decide to use to create the control.

After adding a control to a form, it automatically receives a name. In the Properties window, the control’s name displays in the (Name) field.

The Name property is in parentheses so that, since it is the most regularly used property, if you alphabetically arrange the names of properties in the Properties window, the (Name) property will be on top. This would help you to easily find it.

The default name of a newly added control reflects the name of its control. To differentiate newly added controls of the same class, the Properties window adds an incremental number. For example, if you click the TextBox button on the Toolbox and click the form, the control would be named TextBox1. If you add a second TextBox control, it would be named TextBox2. This causes the default names to be incremental. Since a program usually consists of many controls, it is usually a good idea to rename your controls and give them meaningful and friendlier names. The name should help you identify what the button is used for.

To change the name of a control, on the Properties window, click the (Name) field, type the desired name and press Enter.

When you add a control to a form, the Forms Designer declares a variable for it. To hold the names of controls on a form, Microsoft Visual Studio 2005 creates and associates an additional file to the form. This file is called Form_Name.Designer.cs and you can open it from the Solution Explorer. When you change the name of a control in the Properties window, the studio also changes that name in the designer file.

After creating a control in the Forms Designer, you can change its name programmatically but you should avoid doing that unless you have a good reason to. To change the name of a control, use the Properties window where you would click the (Name) field and type the desired name. If you change the name of a control in the Properties window, the studio automatically makes the necessary changes in the designer file but, if you had used the previous name in your code, you must manually update your code: the studio would not do it for you.

If you are creating a control with code, after declaring its variable and allocating memory for it, you can access its Name property and assign it a string as the name. The name must follow the rules of C# names. Here is an example:

public class Exercise Inherits Form
    private Dim btnSubmit as Button

    private void InitializeComponent()
        btnSubmit = new Button();
        btnSubmit.Name = "Submit";

        this.Controls.Add(btnSubmit);
    End
End

To programmatically change the name of a control, access its Name property and assign a string, using the C# rules of variable names. To retrieve the name of a control, access its Name property.