NULL reference exception

Dwizz · June 20th, 2005, 06:02 AM

Hey,
I keep getting the error NullReferenceException at runtime when trying to save to a database, on the database I've set the fields to accept Null values.
I've tried using the Try ... Catch ... Finally statement but no luck,
is there another way to resolve this problem?
The database is MS Access 2000.
NOTE if the field has values then it saves to the database no problem. The problem only arises when some fields are left null.

As always all help is greatly appreciated.

D

planoie · June 20th, 2005, 08:01 AM

Can you post your table structure and the relevant lines of code for the insert?

-Peter

Dwizz · June 20th, 2005, 08:28 AM

Table Structure is as follows

QuoteID AutoNumber Allow Null = False
Server Text(20) Allow Null = False
NoCPU Integer Allow Null = False
RAID Text Allow Null = True
RAIDType Text Allow Null = True

Code for Inserting into MS Access DB

Code:

Function ServerSpec( _
                ByVal server As String,  _
                ByVal noCPU As Integer,  _
                ByVal rAID As String,  _
                ByVal rAIDType As String,  _
                ) As Integer
        Dim connectionString As String = "Provider=Microsoft.Jet.OLEDB.4.0; Ole DB Services=-4; Data Source=C:\Documents and Settings\quote.mdb"
        Dim dbConnection As System.Data.IDbConnection = New System.Data.OleDb.OleDbConnection(connectionString)

        Dim queryString As String = "INSERT INTO [Quotes] ([Server], [NoCPU], [RAID], [RAIDType]) VALUES (@Server, @NoCPU, @RAID, @RAIDType)"
        Dim dbCommand As System.Data.IDbCommand = New System.Data.OleDb.OleDbCommand
        dbCommand.CommandText = queryString
        dbCommand.Connection = dbConnection

        Dim dbParam_server As System.Data.IDataParameter = New System.Data.OleDb.OleDbParameter
        dbParam_server.ParameterName = "@Server"
        dbParam_server.Value = server
        dbParam_server.DbType = System.Data.DbType.String
        dbCommand.Parameters.Add(dbParam_server)
        Dim dbParam_noCPU As System.Data.IDataParameter = New System.Data.OleDb.OleDbParameter
        dbParam_noCPU.ParameterName = "@NoCPU"
        dbParam_noCPU.Value = noCPU
        dbParam_noCPU.DbType = System.Data.DbType.Int32
        dbCommand.Parameters.Add(dbParam_noCPU)
        Dim dbParam_rAID As System.Data.IDataParameter = New System.Data.OleDb.OleDbParameter
        dbParam_rAID.ParameterName = "@RAID"
        dbParam_rAID.Value = rAID
        dbParam_rAID.DbType = System.Data.DbType.String
        dbCommand.Parameters.Add(dbParam_rAID)
        Dim dbParam_rAIDType As System.Data.IDataParameter = New System.Data.OleDb.OleDbParameter
        dbParam_rAIDType.ParameterName = "@RAIDType"
        dbParam_rAIDType.Value = rAIDType
        dbParam_rAIDType.DbType = System.Data.DbType.String
        dbCommand.Parameters.Add(dbParam_rAIDType)

        Dim rowsAffected As Integer = 0
        dbConnection.Open
        Try
            rowsAffected = dbCommand.ExecuteNonQuery
        Finally
            dbConnection.Close
        End Try

        Return rowsAffected
    End Function

Sub ImageButton1_Click(sender As Object, e As ImageClickEventArgs)

ServerSpec( _
                (DropDownList1.SelectedItem.Value), _
                (DropDownList2.SelectedItem.Value), _
                (DropDownList3.SelectedItem.Value), _
                (DropDownList4.SelectedItem.Value), _
                msgbox("Quote Saved Successfully, QuoteID =" & Quote)

End Sub

cliffd64 · June 21st, 2005, 07:15 AM

Looking at your table definition, the only field that is ALLOWED to be a NULL is the RAID field. If any other field is NULL value, this will cause an error when attempting to insert a record. Try setting the REST of the fields to "Allow NULL = TRUE" if you wish to allow null values.