I am trying to use sql to sum a column in my access database and put the result of this in a text box. The code I have got is the following, but this is coming up with the error below.
Error : Conversion from type 'DBNull' to type 'String' is not valid.
dbCommand = New OleDbCommand dbCommand.Connection = New OleDbConnection(DataBase) dbCommand.Connection.Open() dbCommand.CommandText = "SELECT SUM(TransactionAmount) FROM Transactions WHERE Budget='" & cmbBudget.Text & "'" Reader = dbCommand.ExecuteReader While Reader.Read TextBox1.Text = Reader.GetValue(0) End While
The (DataBase) reference is working correctly, as there is a previous SQL command above this one.
Any help much appreciated!!!!!