c# - app.config custom configuration - 'System.TypeInitializationException' -

i tried following instruction app.config custom configuration

however, got stuck. app.config code:

<?xml version="1.0" encoding="utf-8"?> <configuration>   <configsections>     <section name="configuration" type="dp.configuration, myassembly" />   </configsections>   <startup>        <supportedruntime version="v4.0" sku=".netframework,version=v4.5.2"/>   </startup>   <configuration       inputloc="c:\input"    /> </configuration> 

here configuration class:

    using system.configuration;      namespace dp     {         public class configuration : configurationsection         {             private static readonly configuration settings = configurationmanager.getsection("configuration") configuration;          public static configuration settings         {                         {                 return settings;             }         }          [configurationproperty("inputloc", isrequired = true)]         [stringvalidator(invalidcharacters = "  ~!@#$%^&*()[]{}/;’\"|", minlength = 1, maxlength = 256)]         public string inputlocation         {             { return (string)this["inputloc"]; }             set { this["inputloc"] = value; }         }     } } 

and when call inputfolder = clientconfiguration.settings.inputlocation; system.typeinitializationexception.

error code:

an unhandled exception of type 'system.typeinitializationexception' occurred in dp.exe  additional information: type initializer 'dp.configuration' threw exception.  system.typeinitializationexception unhandled   _hresult=-2146233036   _message=the type initializer 'dp.configuration' threw exception.   hresult=-2146233036   istransient=false   message=the type initializer 'dp.configuration' threw exception.   source=dp   typename=dp.configuration   stacktrace:        @ dp.configuration.get_settings()        @ dp.program.main(string[] args) in c:\program.cs:line 1012        @ system.appdomain._nexecuteassembly(runtimeassembly assembly, string[] args)        @ microsoft.visualstudio.hostingprocess.hostproc.runusersassembly()        @ system.threading.executioncontext.runinternal(executioncontext executioncontext, contextcallback callback, object state, boolean preservesyncctx)        @ system.threading.executioncontext.run(executioncontext executioncontext, contextcallback callback, object state, boolean preservesyncctx)        @ system.threading.executioncontext.run(executioncontext executioncontext, contextcallback callback, object state)        @ system.threading.threadhelper.threadstart()   innerexception: system.configuration.configurationerrorsexception        _hresult=-2146232062        _message=an error occurred creating configuration section handler configuration: not load file or assembly 'myassembly' or 1 of dependencies. system cannot find file specified.        hresult=-2146232062        istransient=false        message=an error occurred creating configuration section handler configuration: not load file or assembly 'myassembly' or 1 of dependencies. system cannot find file specified. (c:\dp.vshost.exe.config line 4)        source=system.configuration        baremessage=an error occurred creating configuration section handler configuration: not load file or assembly 'myassembly' or 1 of dependencies. system cannot find file specified.        filename=c:\dp.vshost.exe.config        line=4        stacktrace:             @ system.configuration.baseconfigurationrecord.findandensurefactoryrecord(string configkey, boolean& isrootdeclaredhere)             @ system.configuration.baseconfigurationrecord.getsectionrecursive(string configkey, boolean getlkg, boolean checkpermission, boolean getruntimeobject, boolean requestishere, object& result, object& resultruntimeobject)             @ system.configuration.baseconfigurationrecord.getsection(string configkey)             @ system.configuration.configurationmanager.getsection(string sectionname)             @ dp.configuration..cctor() in c:\\configuration.cs:line 7        innerexception: system.io.filenotfoundexception             _hresult=-2147024894             _message=could not load file or assembly 'myassembly' or 1 of dependencies. system cannot find file specified.             hresult=-2147024894             istransient=false             message=could not load file or assembly 'myassembly' or 1 of dependencies. system cannot find file specified.             source=system.configuration             filename=myassembly             fusionlog==== pre-bind state information === log: displayname = myassembly  (partial) wrn: partial binding information supplied assembly: wrn: assembly name: myassembly | domain id: 1 wrn: partial bind occurs when part of assembly display name provided. wrn: might result in binder loading incorrect assembly. wrn: recommended provide specified textual identity assembly, wrn: consists of simple name, version, culture, , public key token. wrn: see whitepaper http://go.microsoft.com/fwlink/?linkid=109270 more information , common solutions issue. log: appbase = file:///c://x64/debug/ log: initial privatepath = null calling assembly : system.configuration, version=4.0.0.0, culture=neutral, publickeytoken=b03f5f7f11d50a3a. === log: bind starts in default load context. log: using application configuration file: c:\dp.vshost.exe.config log: using host configuration file:  log: using machine configuration file c:\windows\microsoft.net\framework64\v4.0.30319\config\machine.config. log: policy not being applied reference @ time (private, custom, partial, or location-based assembly bind). log: attempting download of new url file:///c://x64/debug/myassembly.dll. log: attempting download of new url file:///c://x64/debug/myassembly/myassembly.dll. log: attempting download of new url file:///c://x64/debug/myassembly.exe. log: attempting download of new url file:///c://x64/debug/myassembly/myassembly.exe.              stacktrace:                  @ system.configuration.typeutil.gettypewithreflectionpermission(iinternalconfighost host, string typestring, boolean throwonerror)                  @ system.configuration.runtimeconfigurationrecord.runtimeconfigurationfactory.init(runtimeconfigurationrecord configrecord, factoryrecord factoryrecord)                  @ system.configuration.runtimeconfigurationrecord.runtimeconfigurationfactory.initwithrestrictedpermissions(runtimeconfigurationrecord configrecord, factoryrecord factoryrecord)                  @ system.configuration.runtimeconfigurationrecord.createsectionfactory(factoryrecord factoryrecord)                  @ system.configuration.baseconfigurationrecord.findandensurefactoryrecord(string configkey, boolean& isrootdeclaredhere)             innerexception:  

see question: configurationsection-stringvalidator-failing

it looks need add default value attribute in configurationproperty attribute, ie.

[configurationproperty("inputloc", isrequired = true, defaultvalue="something")]