如何在app.config中获取自定义部分的intellisense？

<?xml version="1.0" encoding="utf-8" ?><configuration>
 <configSections>
   <section name="MyCustomSection" type="System.Configuration.NameValueSectionHandler" />
  </configSections>
  <MyCustomSection>
    <add key="MyKey" value="MyValue" />
  </MyCustomSection>
</configuration>

<?xml version="1.0" encoding="utf-8"?>
<xs:schema id="MyCustomSection"
    elementFormDefault="qualified"
    xmlns="http://schemas.microsoft.com/MyCustomSection"
    xmlns:mcs="http://schemas.microsoft.com/MyCustomSection"
    xmlns:xs="http://www.w3.org/2001/XMLSchema"
    targetNamespace="http://schemas.microsoft.com/MyCustomSection">

  <xs:element name="MyCustomSection">
    <xs:complexType>
      <xs:sequence>
        <xs:element name="add" minOccurs="0" maxOccurs="unbounded">
          <xs:complexType>
            <xs:attribute name="key" type="xs:string" use="required" />
            <xs:attribute name="value" type="xs:string" use="required" />
          </xs:complexType>
        </xs:element>
      </xs:sequence>
    </xs:complexType>
  </xs:element>
</xs:schema>

<?xml version="1.0" encoding="utf-8" ?><configuration>
 <configSections>
   <section name="MyCustomSection" type="System.Configuration.NameValueSectionHandler" />
  </configSections>
  <MyCustomSection xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="MyCustomSection.xsd">
    <add key="MyKey" value="MyValue" />
  </MyCustomSection>
</configuration>

var configuration = ConfigurationManager.GetSection("MyCustomSection") as NameValueCollection;
var myValue = configuration["MyKey"];