Today I experienced the following issue:

I had a class where I would open a SqlConnection, do some actions, and then in the deconstructor I closed the SqlConnection.

~Dumper()
{
    this._sqlConnection.Close();
}

Unfortunately every time my program ran it stopped with this error:

Internal .Net Framework Data Provider error 1.

(click to enlarge)

Well it seems that you cannot close a SqlConnection in a ~Deconstructor block.

So the solution is implementing the IDisposable interface

internal class Dumper : IDisposable
{
    private readonly SqlConnection _sqlConnection;

    public Dumper()
    {
        //build and open the connection
        this._sqlConnection = new SqlConnection(Settings.Default.ConnectionString);
        this._sqlConnection.Open();
    }

    /// <summary>
    /// Some function
    /// </summary>
    /// <param name="param">param</param>
    public void SomeFunction(SomeParameter param)
    {
    }

    public void Dispose()
    {
        this._sqlConnection.Close();
    }
}

And to use it you do this:

using (Dumper dumper = new Dumper())
{
    dumper.SomeFunction(myParam);
}

This will cause dumper to be Disposed after the } and it will no longer be available