raur
У вас написан код, не имеющий особого смысла
MSDN SqlCommand.ExecuteNonQuery MethodSqlCommand.ExecuteNonQuery Method
Executes a Transact-SQL statement against the connection and returns the number of rows affected.
You can use the ExecuteNonQuery to perform catalog operations (for example, querying the structure of a database or creating database objects such as tables), or to change the data in a database without using a DataSet by executing UPDATE, INSERT, or DELETE statements.

Although the ExecuteNonQuery does not return any rows , any output parameters or return values mapped to parameters are populated with data.

For UPDATE, INSERT, and DELETE statements, the return value is the number of rows affected by the command. For all other types of statements, the return value is -1. If a rollback occurs, the return value is also -1.

Кроме того всегда лучше явно перечислять список колонок.