Question

I’m trying to handle DBNull exception while reading data from database.
It’s my code:

...
Dim SQLRDAs SqlDataReader
...
val1= GetStringFromDB(Trim(SQLRD("Name")))
val2= GetStringFromDB(Trim(SQLRD("Level")))
val2= GetStringFromDB(Trim(SQLRD("blahblah")))
...
Public Function GetStringFromDB(ByVal inputValue) As String
     Dim outputValue As String

     If IsDBNull(inputValue) Then
         outputValue = "null"
     Else
         outputValue = inputValue
     End If

     Return outputValue
End Function

But still I get Conversion from type 'DBNull' to type 'String' is not valid. error. What’s wrong?

Answer 1

IsDBNull checks if a value is missing. It is not equivalent to Nothing or to String.Empty.
Are you sure that your inputValue contains DBNull.Value?

I will change your code in this way:

 If String.IsNullOrEmpty(inputValue) OrElse IsDBNull(inputValue) Then 
     outputValue = "null" 

Also note that you don’t specify the type of inputValue, in my answer I assume As String