Custom configuration section in app.config cannot read xml data as collection in C# application

Question

I have following class extended ApplicationSettingsBase as below

public class SMTPServerConfig : ApplicationSettingsBase
{
    private static SMTPServerConfig instance = (SMTPServerConfig)Synchronized(new SMTPServerConfig());

    public static SMTPServerConfig Instance { get { return instance; } }

    [ApplicationScopedSetting]
    [DefaultSettingValue("")]
    [SettingsSerializeAs(System.Configuration.SettingsSerializeAs.Xml)]
    public List<SMTPServerConfigItem> SMTPServers
    {
        get
        {
            return ((List<SMTPServerConfigItem>)(this["SMTPServers"]));
        }
    }

    [ApplicationScopedSetting]
    [DefaultSettingValue("")]
    [SettingsSerializeAs(System.Configuration.SettingsSerializeAs.String)]
    public string TestProp
    {
        get
        {
            return ((string)(this["TestProp"]));
        }
    }
}

[Serializable]
public class SMTPServerConfigItem
{
    
    public string SMTPHost { get; set; }
    public string SMTPPort { get; set; }
    public string SMTPAccount { get; set; }
    public string SMTPPassword { get; set; }
}

Here is my 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="Example.Config.SMTPServerConfig" type="System.Configuration.ClientSettingsSection, System, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" requirePermission="false" />
    </sectionGroup>

  </configSections>


  <applicationSettings>
    <Example.Config.SMTPServerConfig>
      <setting name="TestProp" serializeAs="String">
        <value>123123</value>
      </setting>
      <setting name="SMTPServers" serializeAs="Xml">
        <value>
          <SMTPServerConfigItem>
            <SMTPHost>smtp.example.com</SMTPHost>
            <SMTPPort>123</SMTPPort>
            <SMTPAccount>[email protected]</SMTPAccount>
            <SMTPPassword>123456</SMTPPassword>
          </SMTPServerConfigItem>

          <SMTPServerConfigItem>
            <SMTPHost>smtp.example.com</SMTPHost>
            <SMTPPort>123</SMTPPort>
            <SMTPAccount>[email protected]</SMTPAccount>
            <SMTPPassword>123456</SMTPPassword>
          </SMTPServerConfigItem>

        </value>

      </setting>
    </Example.Config.SMTPServerConfig>
  </applicationSettings>

</configuration>

When i use SMTPServerConfig.Instance.TestProp it will show result is "123123" (it's true value, it mean i have correct config's schema for it), but SMTPServerConfig.Instance.SMTPServers.Count always zero. Where i'm wrong in code or config file ?

Answer 1

After a hours of research, i found a question in stackoverflow then i know where i'm wrong. I was missing a xml tag in app.config file. Question: Trying to create a custom partial settings file

Then now i will correct my App.config file

<?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="Example.Config.SMTPServerConfig" type="System.Configuration.ClientSettingsSection, System, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" requirePermission="false" />
    </sectionGroup>

  </configSections>


  <applicationSettings>
    <Example.Config.SMTPServerConfig>
      <setting name="TestProp" serializeAs="String">
        <value>123123</value>
      </setting>
      <setting name="SMTPServers" serializeAs="Xml">
        <value>
          <ArrayOfSMTPServerConfigItem>
            <SMTPServerConfigItem>              
              <SMTPHost>smtp.example.com</SMTPHost>
              <SMTPPort>123</SMTPPort>
              <SMTPAccount>[email protected]</SMTPAccount>
              <SMTPPassword>123456</SMTPPassword>
            </SMTPServerConfigItem>

            <SMTPServerConfigItem>              
              <SMTPHost>smtp.example.com</SMTPHost>
              <SMTPPort>123</SMTPPort>
              <SMTPAccount>[email protected]</SMTPAccount>
              <SMTPPassword>123456</SMTPPassword>
            </SMTPServerConfigItem>
          </ArrayOfSMTPServerConfigItem>

        </value>

      </setting>
    </Example.Config.SMTPServerConfig>
  </applicationSettings>

</configuration>

After add ArrayOfSMTPServerConfigItem tag, it will solve this problem.