Configuration System Failed To Initialize

In my application when I try to get the connection string by using this code :

 System.Configuration.ConfigurationManager.ConnectionStrings["ConStr"].ConnectionString;

It throws an exception that "Configuration System Failed To Initialize". Where is the format of app.config wrong ?

 <?xml version="1.0"?>
    <configuration>


      <connectionStrings>
        <add name="ConStr" connectionString="Integrated Security=false;Persist Security Info=False;User ID=funny;password=veryfunny;Initial Catalog=vegimanager;Data Source=.\sqlexpress;"/>
      </connectionStrings>



      <configSections>
        <sectionGroup name="userSettings" type="System.Configuration.UserSettingsGroup, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089">
          <section name="Vegi_Manager.Properties.Settings" type="System.Configuration.ClientSettingsSection, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" allowExeDefinition="MachineToLocalUser" requirePermission="false"/>
        </sectionGroup>
      </configSections>




      <userSettings>
        <Vegi_Manager.Properties.Settings>
          <setting name="FIRMNAME" serializeAs="String">
            <value/>
          </setting>
          <setting name="FIRMADDRESS" serializeAs="String">
            <value/>
          </setting>
          <setting name="FIRMCITY" serializeAs="String">
            <value/>
          </setting>
          <setting name="FIRMSTATE" serializeAs="String">
            <value/>
          </setting>
          <setting name="FIRMPHONE" serializeAs="String">
            <value/>
          </setting>
          <setting name="FIRMMOBILE" serializeAs="String">
            <value/>
          </setting>
          <setting name="FIRMEMAIL" serializeAs="String">
            <value/>
          </setting>
          <setting name="FIRMTIN" serializeAs="String">
            <value/>
          </setting>
          <setting name="FIRMPAN" serializeAs="String">
            <value/>
          </setting>
          <setting name="FIRMMANDITAXNO" serializeAs="String">
            <value/>
          </setting>
          <setting name="INITIALFONFIGDONE" serializeAs="String">
            <value>False</value>
          </setting>
          <setting name="FIRMJURISDICTION" serializeAs="String">
            <value/>
          </setting>
          <setting name="FIRMBANKDETAILS" serializeAs="String">
            <value/>
          </setting>
          <setting name="FIRMDETAILS" serializeAs="String">
            <value/>
          </setting>
          <setting name="BILLFORMATNO" serializeAs="String">
            <value>0</value>
          </setting>
          <setting name="PRINTERNAME" serializeAs="String">
            <value/>
          </setting>
        </Vegi_Manager.Properties.Settings>
      </userSettings>



      <startup>
        <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.0"/>
      </startup>
    </configuration>