Hello chaps, I am writing a VB.Net program to retreive the database field values from a table in which several columns may contain "no values" in some rows.
Database format: "Access"
Error message: A first chance exception of type 'System.InvalidCastException' occurred in Microsoft.VisualBasic.dllmy progam failed while running these few lines.
---------Code-------
Dim s_BurialAft As String
Dim s_BurialType As String
Dim s_Depth As String.....
Do While Not pTableRow is nothing
.....
'error occurs when it runs to the below lines_BurialAft = pTableRow.Value(i_xBurialAft) 'i_x_BurialAft is the column index no s_BurialType = pTableRow.Value(i_xBurialType) '_xBurialType is the column index no
s_Depth = pTableRow.Value(i_xDepth) 'i_xDepth is the column index no
.....
pTableRow = pTableRow.NextRow
Loop--- end of code ---
But when i converted the few lines of codes:
s_BurialAft = CType(pTableRow.Value(i_xBurialAft), String)
s_BurialType = CType(pTableRow.Value(i_xBurialType), String)
s_Depth = CType(pTableRow.Value(i_xDepth), String)
Error message: (Same message)
A first chance exception of type 'System.InvalidCastException' occurred in Microsoft.VisualBasic.dllCan anybody find out what problem here. Or how to test null / no values out before assigning to the string variables.
Thanks a lot!
E Lau
Hello I found out the following in the Access Table. Some tables refers the "no value" fields as <Null>. But some tables refers the "no value" field as "" (blank)
Error message: A first chance exception of type 'System.InvalidCastException' occurred in Microsoft.VisualBasic.dll
So, I test whether the field values of the columns are null or not now.
If Convert.IsDBNull(pTableRow.Value(i_xBurialAft)) Then
s_BurialAft = ""
Else
s_BurialAft = pTableRow.Value(i_xBurialAft)
End If
If Convert.IsDBNull(pTableRow.Value(i_xBurialType)) Then
s_BurialType = ""
Else
s_BurialType = pTableRow.Value(i_xBurialType)
End If
If Convert.IsDBNull(pTableRow.Value(i_xDepth)) Then
s_Depth = ""
Else
s_Depth = pTableRow.Value(i_xDepth)
End IfIt is fine and successful.
Thanks
E Lau
Yes (14) | ![]() | |
No (14) | ![]() | |
I don't know (15) | ![]() |