6.6 Save the Size and Location of a Form

Problem

You need to store the size and position of a resizable form and restore it the next time the form is shown.

Solution

Store the Left , Top , Width , and Height form properties in the Windows registry.

Discussion

The Windows registry is an ideal place for storing position and size information for a form. Typically, you'll store information about each form in a separate key, perhaps using the class name of the form. These keys will be stored under an application-specific key.

To automate this process, it helps to create a dedicated class that saves and retrieves form settings. The FormSettingStore class shown in the following example fills this role. This class provides a SaveSettings method that accepts a form and writes its size and position information to the registry, as well as an ApplySettings method that accepts a form and applies the settings from the registry. The registry key path and the name of the form subkey are stored as class member variables .

 using System; using System.Windows.Forms; using Microsoft.Win32; public class FormSettingStore {     private string regPath;     private string formName;     private RegistryKey key;     public string RegistryPath {         get {return regPath;)     }     public string FormName {         get {return formName;}     }     public FormSettingStore(string registryPath, string formName) {              this.regPath = registryPath;         this.formName = formName;         // Create the key if it doesn't exist.         key = Registry.LocalMachine.CreateSubKey(registryPath + formName);     }     public void SaveSettings(System.Windows.Forms.Form form) {              key.SetValue("Height", form.Height);         key.SetValue("Width", form.Width);         key.SetValue("Left", form.Left);         key.SetValue("Top", form.Top);     }     public void ApplySettings(System.Windows.Forms.Form form) {              // If form settings are not available, the current form settings         // are used instead.         form.Height = (int)key.GetValue("Height", form.Height);         form.Width = (int)key.GetValue("Width", form.Width);         form.Left = (int)key.GetValue("Left", form.Left);         form.Top = (int)key.GetValue("Top", form.Top);     } }

To use the FormSettingStore class, simply add the event-handling code shown here to any form. This code saves the form properties when the form closes and restores them when the form is loaded.

 private FormSettingStore formSettings; private void Form1_Load(object sender, System.EventArgs e) {     formSettings = new FormSettingStore(@"Software\MyApp\", this.Name);     formSettings.ApplySettings(this); } private void Form1_Closed(object sender, System.EventArgs e) {     formSettings.SaveSettings(this); }

Note

Remember that access to the registry can be limited based on the current Windows user account and code access security policy. When you create an application that requires registry access, it's a good practice to document the fact that the assembly requires access to the registry by using a minimum permission request, as described in recipe 13.7.