I am a beginner trying to make a networked game called Guess Who.
I have 2 combo boxes
I am trying to read an access database. Whatever is selected in the 1st combo box will be the column to 'lookup' the values in the database. These values should go into the 2nd combo box. I keep getting this error:"Conversion from type 'DBNull' to type 'String' is not valid" on line "Category = Reader.Item(Columns)" when I select "Eye Color" in the 1st combo box. I'm guessing its because its reading the null value after reading "Brown".
How do you stop this from happening?
My database looks like the following:
The column names are in between the [ ] sorry don't know how to format this..
- Code: Select all
[Eye Color] [Hair Color]
Blue Black
Brown Blonde
Brown
Red
This is the code I have to read the database:
- Code: Select all
Public Sub Question_Update()
Dim Cmd As OleDb.OleDbCommand
Dim Con As OleDb.OleDbConnection
Dim Sql As String = Nothing
Dim Reader As OleDb.OleDbDataReader
Dim ComboRow As Integer = -1
Dim Columns As Integer = 0
Dim Category As String = Nothing
Dim based As String = cmbFeatures.Text
cmbQuestion.Items.Clear()
Con = New OleDb.OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=|DataDirectory|\Questions.mdb")
Sql = "SELECT" & " [" & based & "] " & "FROM [Questions]"
Cmd = New OleDb.OleDbCommand(Sql, Con)
Con.Open()
Reader = Cmd.ExecuteReader()
While Reader.Read()
For Columns = 0 To Reader.FieldCount - 1
Category = Reader.Item(Columns) 'READ COLUMN FROM DATABASE
Next
cmbQuestion.Items.Add(Category)
ComboRow += 1
End While
Con.Close()
End Sub
