Exception using SQLiteDataReader

Question

I'm making a Custom SQLite Wrapper. This is meant to allow a presistent connection to a database. However, I receive an exception when calling this function twice.

public Boolean DatabaseConnected(string databasePath)
{
    bool exists = false;
    if (ConnectionOpen())
    {
        this.Command.CommandText = string.Format(DATABASE_QUERY);
        using (reader = this.Command.ExecuteReader())
        {
            while (reader.Read())
            {
                if (string.Compare(reader[FILE_NAME_COL_HEADER].ToString(), databasePath, true) == 0)
                {
                    exists = true;
                    break;
                }
            }
            reader.Close();
        }
    }
    return exists;
}

I use the above function to check if the database is currently open before executing a command or trying to open a database. The first time I execute the function, it executes with no issue. After that the reader = this.Command.ExecuteReader() throws an exception

Object reference not set to an instance of an object.
StackTrace:
   at System.Data.SQLite.SQLiteStatement.Dispose()
   at System.Data.SQLite.SQLite3.Reset(SQLiteStatement stmt)
   at System.Data.SQLite.SQLite3.Step(SQLiteStatement stmt)
   at System.Data.SQLite.SQLiteDataReader.NextResult()
   at System.Data.SQLite.SQLiteDataReader..ctor(SQLiteCommand cmd, CommandBehavior behave)
   at System.Data.SQLite.SQLiteCommand.ExecuteReader(CommandBehavior behavior)
   at System.Data.SQLite.SQLiteCommand.ExecuteReader()
   at EveTraderApi.Database.SQLDatabase.DatabaseConnected(String databasePath) in C:\Documents and Settings\galford13x\My Documents\Visual Studio 2008\Projects\EveTrader\EveTraderApi\Database\Database.cs:line 579
   at EveTraderApi.Database.SQLDatabase.OpenSQLiteDB(String filename) in C:\Documents and Settings\galford13x\My Documents\Visual Studio 2008\Projects\EveTrader\EveTraderApi\Database\Database.cs:line 119
   at EveTraderApiExample.Form1.CreateTableDataTypes() in C:\Documents and Settings\galford13x\My Documents\Visual Studio 2008\Projects\EveTrader\EveTraderApiExample\Form1.cs:line 89
   at EveTraderApiExample.Form1.Button1_ExecuteCommand(Object sender, EventArgs e) in C:\Documents and Settings\galford13x\My Documents\Visual Studio 2008\Projects\EveTrader\EveTraderApiExample\Form1.cs:line 35
   at System.Windows.Forms.Control.OnClick(EventArgs e)
   at System.Windows.Forms.Button.OnClick(EventArgs e)
   at System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)
   at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
   at System.Windows.Forms.Control.WndProc(Message& m)
   at System.Windows.Forms.ButtonBase.WndProc(Message& m)
   at System.Windows.Forms.Button.WndProc(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
   at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
   at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
   at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(Int32 dwComponentID, Int32 reason, Int32 pvLoopData)
   at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
   at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
   at System.Windows.Forms.Application.Run(Form mainForm)
   at EveTraderApiExample.Program.Main() in C:\Documents and Settings\galford13x\My Documents\Visual Studio 2008\Projects\EveTrader\EveTraderApiExample\Program.cs:line 18
   at System.AppDomain._nExecuteAssembly(Assembly assembly, String[] args)
   at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
   at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
   at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
   at System.Threading.ThreadHelper.ThreadStart()

Answer 1

You could have a custom wrapper to manage connections but this wrapper should not manage commands: this.Command. As the command object is stored within your wrapper it will be reused. The problem is that the first time you call ExeuteReader this command is disposed and the second time you call it you get the exception. Try creating the commands for each query:

public bool DatabaseConnected(string databasePath)
{
    if (ConnectionOpen())
    {
        using (var command = YourSQLiteConnection.CreateCommand())
        {
            command.CommandText = string.Format(DATABASE_QUERY);
            using (reader = command.ExecuteReader())
            {
                while (reader.Read())
                {
                    if (string.Compare(reader[FILE_NAME_COL_HEADER].ToString(), databasePath, true) == 0)
                    {
                        return true;
                    }
                }
            }
        }
    }
    return false;
}