If the configuration file contains a configsections element, the configsections element must be the first child element of the configuration element. After placing the appsettings in configsections, it is normal.
The elements in the configsections must correspond to the following custom configuration section one by one.
For example, there are 4 custom configuration sections below, but there are only 3 in configsections, and an error occurs: The configuration system failed to initialize.
<configSections>
<section name= "A_f63_structure" type= "A_f63_structurehandler,pkgbuilder"/>
<section name= "A_f10_structure" type= "A_f10_structurehandler,pkgbuilder"/>
<section name= "A_f11_structure" type= "A_f11_structurehandler,pkgbuilder"/>
</configSections>
<C_F10_Structure>
</C_F10_Structure>
<A_F63_Structure>
</A_F63_Structure>
<A_F10_Structure>
</A_F10_Structure>
<A_F11_Structure>
</A_F11_Structure>
From: http://www.cnblogs.com/edong/archive/2010/08/05/1793301.html
There was an error with the App. Config file and the configuration system failed to initialize. Problem Solving Solutions