>I have an app.config file with a tag for an email address. I'd like to change the email address at runtime and have it saved to the config file. Any ideas on how to do this?
>
>Here's my codel:
>

><?xml version="1.0" encoding="utf-8" ?>
><configuration>
>    <configSections>
>        <sectionGroup name="userSettings" type="System.Configuration.UserSettingsGroup, System, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" >
>            <section name="FlexTime.Properties.Settings" type="System.Configuration.ClientSettingsSection, System, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" allowExeDefinition="MachineToLocalUser" requirePermission="false" />
>        </sectionGroup>
>    </configSections>
>  <connectionStrings>
>    <add name="FlexTime.Properties.Settings.InCheckConnectionString"
>      connectionString="Data Source=SVNYDBSQLDEV1;Initial Catalog=InCheck;Integrated Security=True"
>      providerName="System.Data.SqlClient" />
>  </connectionStrings>
>  <appSettings>
>        <add key="server" value="172.16.202.66" />
>        <add key="supvemail" value="jweil@nyhomes.org" />
>        <add key="title" value="FlexTime" />
>        <add key="conString" value="Initial Catalog=InCheck;Data Source=SVNYDBSQLDEV1;Integrated Security=SSPI;" />
>    </appSettings>
>  <userSettings>
>    <FlexTime.Properties.Settings>
>      <setting name="supvemail" serializeAs="String">
>        <value>jweil@nyhomes.org</value>
>      </setting>
>      <setting name="title" serializeAs="String">
>        <value>FlexTime</value>
>      </setting>
>    </FlexTime.Properties.Settings>
>  </userSettings>
></configuration>
>

>The code in my form.cs is this:
>
>ConfigurationSettings.AppSettings["supvemail"] = this.txtSupervisorEmail.Text.Trim();
>
>The value isn't saved and reverts back to the old application setting once the application is relaunched.

See Configuration.Save() in docs (also check ConfigurationSaveMode enum)