Using Settings in C#

Introduction

The .NET Framework 2.0 allows you to create and access values that are persisted between application execution sessions. These values are called settings. Settings can represent user preferences, or valuable information the application needs to use. For example, you might create a series of settings that store user preferences for the color scheme of an application. Or you might store the connection string that specifies a database that your application uses. Settings allow you to both persist information that is critical to the application outside of the code, and to create profiles that store the preferences of individual users.

While Visual Basic 2005 has provided an easily discoverable mechanism for accessing settings using the My namespace, there is no analogous namespace in Visual C# 2005, and thus settings are somewhat more difficult to access. Nonetheless, C# users can still use settings by accessing the Properties namespace. In the course of this article, you will learn the difference between application and user settings, how to create new settings at design time, how to access settings at run time, and even how to incorporate multiple sets of settings into your application.


Application and User Settings

Settings have four properties:

•  Name: The Name property of settings is the name that is used to access the value of the setting at run time.
• Type: The Type of the setting is the .NET Framework type that the setting represents. A setting can be of any type. For example, a setting that holds a user preference of color would be a System.Color type.
• Scope: The Scope property represents how a setting can be accessed at run time. There are two possible values for the Scope property: Application and User. These will be discussed more in this section.
• Value: The Value property represents the value returned when the setting is accessed. The value will be of the type represented by the Type property.

Of these properties, most are fairly self-explanatory. Name, Type, and Value are all concepts that should be familiar to most programmers. The Scope property requires a little more explanation. Settings have two possible scopes: application scope and user scope. Settings with application scope represent settings that are used by the application regardless of user preferences, whereas settings with user scope are generally less important to the actual application and are more likely to be associated with preferences or other non-critical values.

The crucial distinction between application-scope and user-scope settings is that user-scope settings are read/write at run time, and their values can be changed and saved in code. Application-scope settings are read only at run time. While they can be read, they cannot be written to. Settings with application scope can only be changed at design time, or by altering the settings file manually.

Creating a New Setting at Design Time

You can create a new setting at design time by using the Settings designer. The Settings designer is a familiar grid-style interface that allows you to create new settings and specify properties for those settings. You must specify Name, Type, Scope, and Value for each new setting. Once a setting is created, it can be assessed in code using the mechanisms described later in this article.

To Create a New Setting at Design Time

1.     In Solution Explorer, expand the Properties node of your project.
2.     In Solution Explorer, double-click the .settings file in which you want to add a new setting. The default name for this file is Settings.settings.
3.     In the Settings designer, set the Name, Type, Scope, and Value for your setting. Each row represents a single setting. Figure 1 shows an example of the Settings designer.

Changing the Value of an Existing Setting at Design Time

You can also use the Settings designer to change the value of a pre-existing setting at design time, as described in the following steps:

To Change the Value of an Existing Setting at Design Time

1.     In Solution Explorer, expand the Properties node of your project.
2.     In Solution Explorer, double-click the .settings file in which you want to add a new setting. The default name for this file is Settings.settings.
3.     In the Settings designer, find the setting you want to change and type the new value in the Value column.

Changing the Value of a Setting Between Application Sessions

At times, you might want to change the value of a setting between application sessions after the application has been compiled and deployed. For example, you might want to change a connection string to point to the correct database location. Since design-time tools are not available after the application has been compiled and deployed, you must change the setting value manually in the file.

App.config

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
    <configSections>
        <sectionGroup name="applicationSettings" type="System.Configuration.ApplicationSettingsGroup, System, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" >
            <section name="setting.Properties.Settings" type="System.Configuration.ClientSettingsSection, System, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" requirePermission="false" />
            <section name="setting.Settings1" type="System.Configuration.ClientSettingsSection, System, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" requirePermission="false" />
        </sectionGroup>
    </configSections>
    <applicationSettings>
        <setting.Properties.Settings>
            <setting name="MyColor" serializeAs="String">
                <value>Blue</value>
            </setting>
        </setting.Properties.Settings>
        <setting.Settings1>
            <setting name="MyColor" serializeAs="String">
                <value>Blue</value>
            </setting>
        </setting.Settings1>
    </applicationSettings>
</configuration>

Using Settings at Run Time

Settings are available to the application through code at run time. You can access the value of settings with application scope on a read-only basis, and you can read and write the values of user-scope settings. Settings are available in C# through the Properties namespace.
Reading Settings at Run Time

You can read both application-scope and user-scope settings at run time with the Properties namespace. The Properties namespace exposes all of the default settings for the project by using the Properties.Settings.Default object. When writing code that uses settings, all settings appear in IntelliSense and are strongly typed. Thus, if you have a setting that is of type System.Drawing.Color, for example, you can use it without having to cast it first, as shown in the following example:

this.BackColor = Properties.Settings.Default.myColor;