"Value cannot be null.\r\nparameter name: providerinvariantname"}, in C# windows form, error dbprovider factorie (dataprovider name) not null how fix these

public static DbCommand CreateCommand()
{ 
            //WebConfigReader 
            // Obtain the database provider name
            string dataProviderName = WebConfigReader.DbProviderName;
            // Obtain the database connection string
            string connectionString = WebConfigReader.DbConnectionString;
            // Create a new data provider factory
            DbProviderFactory factory = DbProviderFactories.GetFactory(dataProviderName);
            // Obtain a database specific connection object
            DbConnection conn = factory.CreateConnection();
            // Set the connection string
            conn.ConnectionString = connectionString;
            // Create a database specific command object
            DbCommand comm = conn.CreateCommand();
            // Set the command type to stored procedure
            comm.CommandType = CommandType.StoredProcedure;
            // Return the initialized command object
            return comm;
        }
    }
}