意外的异常：System.TypeInitializationException

Question

using c#, .Net Framework 4.5

Try to crete simple programm with next code:

 enum DataProvider { Sqlserver, Obdc, Oledb, None }

class Program
{
    static void Main(string[] args)
    {
        Console.WriteLine("simple database connection factory");
        IDbConnection Idbc = GetConnection(DataProvider.Sqlserver);
        Console.WriteLine("your connection - {0}", Idbc.GetType().Name);
        Console.ReadLine();
    }
    private static IDbConnection GetConnection(DataProvider dataProvider)
    {
        IDbConnection connection = null;
        switch (dataProvider)
        {
            case DataProvider.Sqlserver:
                connection = new SqlConnection();
                break;
            case DataProvider.Oledb:
                connection = new OleDbConnection();
                break;
            case DataProvider.Obdc :
                connection = new OdbcConnection();
                break;
        }
        return connection;
    }
}

First time it's run ok - gor required result, but now get Exceptions: System.TypeInitializationException on string connection = new SqlConnection(); .

See help in MSDN but can find only When a class initializer fails to initialize a type, a TypeInitializationException is created and passed a reference to the exception thrown by the type's class initializer But whats is reason for fail to initialize a type? why first time it's runned ok and second time i got error?

Answer 1

As mentioned by Ahmet Kakıcı - check inner exception - like sown on pic below

found, a lot of innered exception and the last one was with description {System.Configuration.ConfigurationException[1]}

Try just reset MyApp.exe.config file (put default values like below :

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
    <startup> 
        <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5" />
    </startup>
</configuration>

As result - now all it's ok.

Real reason whats happend with .config file - really don't know...