Invalid row handle

[brd24gor]

I am trying to to retrieve a value from a table called Session_ID. When the line in my try block is executed, I get a "Row handle is invalid" error. The value I am trying to get is a long integer in an Access database. I have also tried a SELECT MAX and it still doesn't work. You guys have any helpful suggestions?

		private int GetSessionNumber()
		{
			//Check database connection.  If closed, open it
			if (aLib.SQLConnection.State==System.Data.ConnectionState.Closed)
				aLib.SQLConnection.Open();

			string sql = "SELECT Session_ID FROM User_Tests " + 
				"WHERE Test_ID = '" + testID + "' AND User_ID = '" + taker.UserID + "' " +
				"ORDER BY Session_ID DESC";
			OleDbCommand getSession = new OleDbCommand(sql,aLib.SQLConnection);
			OleDbDataReader sessionReader = getSession.ExecuteReader();
			sessionReader.Read();
			//MessageBox.Show(Convert.ToString((int)sessionReader.GetValue(0)));
			try
			{
				int sessionID = sessionReader.GetInt32(0); 
			} 
			catch(Exception e) { MessageBox.Show(e.ToString()); }
			sessionReader.Close();
			//return(sessionID);
			return 0;
		}

 

[wooody1245]

Is Session_ID an integer? Maybe you should try using sessionReader.GetValue(0) instead of sessionReader.GetInt32(0);

 

[brd24gor]

Yeah, it is defined as a long integer field in the database. I tried the GetValue method in the commented out MessageBox.Show line and still had an error. I am trying to use the ExecuteScalar() and SQL SELECT MAX right now, but I keep getting a "Specified cast is not valid" error on my ExecuteScalar() statement:

		private int GetSessionNumber()
		{
			//Check database connection.  If closed, open it
			if (aLib.SQLConnection.State==System.Data.ConnectionState.Closed)
				aLib.SQLConnection.Open();

			string sql = "SELECT MAX(Session_ID) As SNum FROM User_Tests " + 
				"WHERE Test_ID = '" + testID + "' AND User_ID = '" + taker.UserID + "'";
				
			OleDbCommand getSession = new OleDbCommand(sql,aLib.SQLConnection);

			try
			{

				int sessionID = (int)getSession.ExecuteScalar();
				MessageBox.Show(Convert.ToString(sessionID));
			} 
			catch(Exception e) { MessageBox.Show(e.ToString()); }

			return 0;
		}

I can't seem to figure out how to cast a MAX statement. I have tried strings and all of the ints and have not had any luck. Any suggestions at this point are greatly apprecited. I have been banging my head on the table on this since last week.

--Brad

 

[chmohan]

Also change
e.ToString()

to e.description ,source,innerexception etc

 

[chiph]

A long int in the database will likely be a 64-bit value. Check your documentation to see.

Chip H.


____________________________________________________________________
Donate to Katrina relief:

http://s1.amazon.com/paypage/PELYGQVJ8Q7IB/103-6821258-5919825

If you want to get the best response to a question, please read FAQ222-2244 first

 

[brd24gor]

I am still getting "Specified cast is not valid" errors for Int16, Int32, and Int64 values. I may just delete and re-create the table to see if the definition is somehow corrupted. I am completely out of ideas if that doesn't work.
Any other ideas?

--Brad

 

[brd24gor]

Wow. All I can say is I am a complete idiot. The problem ended up being with one of the variables in my SQL statement. It is pretty hard to cast a value from a query that doesn't return anything

I apologize for taking up valuable time for anyone who tried to help. Thanks again!

--Brad

 

[chmohan]

why do you convert it at the start?

try
string sTest = getSession.ExecuteScalar().ToString();
MessageBox.Show(sTest);

and see what it gives you,cant you debug this using breakpoint and quickwatch?

 

[brd24gor]

The MessageBox after the ExecuteScalar() call was for debugging purposes and will not be part of the program. This is why I casted as an int and then converted it to a string for the MessageBox. The method will eventually return sessionID.

--Brad