Checking 3rd character with Char.IsNumber in vb.net - sql

Question

I am searching a database and pulling results from it. Before displaying it in WPF I am checking the contents of the text in a field called PrimarySponsor which can be (1) blank/null (2) number at 3rd character (3) persons name. I am currently using Char.IsNumber to check option 2 if there is a number at position 4.
If reader("PrimarySponsor") Is DBNull.Value Then
resultxPrimSpon = ""
ElseIf Char.IsNumber(reader("PrimarySponsor"), 3) Then
resultxPrimSpon = "Terminated"
Else
resultxPrimSpon = reader("PrimarySponsor")
End If
Before I put the Char.IsNumber check in I was getting 4 results displaying. When i add the Char.IsNumber code I only get 2 results along with the error;
Error while connecting to SQLServer.Sepcified argument was out of the range of valid values. Parameter name: index.
Anyone have any ideas about why this is happening or how to work around it?

Answer 1

It's not clear where you get that error because Char.IsNumber is not a sql-server method. So i assume that it's a custom message from you. However, the "Specified argument was out of the range" is documented:
ArgumentOutOfRangeException: index is less than zero or greater than
the last position in s.
So it seems that at least one of the strings is shorter than 4 characters. In general you should store the reader values in a variable of the correct type if you have to access it more than once. In this case in a String-variable.
But it's also a good idea to create a custom type that has all properties. Then you can add all to a List(Of T). Here's an example:
Public Class Sponsor
Public Property PrimarySponsor As String
End Class
Of course you could also fill a List(Of String) instead of a List(Of Sponsor). Then you don't need to create a new type. But i assume that you have more than one column in the table. Using a custom type increases readability and maintainability much.
....
Dim allSponsors As New List(Of Sponsor)
Using reader = command.ExecuteReader()
If reader.HasRows Then
Dim primSponsorColumnIndex = reader.GetOrdinal("PrimarySponsor")
While reader.Read
Dim sponsor As New Sponsor()
If reader.IsDBNull(primSponsorColumnIndex) Then
sponsor.PrimarySponsor = ""
Else
sponsor.PrimarySponsor = reader.GetString(primSponsorColumnIndex)
If sponsor.PrimarySponsor.Length >= 4 AndAlso _
Char.IsDigit(sponsor.PrimarySponsor(3)) Then
sponsor.PrimarySponsor = "Terminated"
End If
End If
allSponsors.Add(sponsor)
End While
End If
End Using
First use DataReader.IsDBNull to check if the value is Null. Then check if Length >= 4 before you use Char.IsDigit(sponsor.PrimarySponsor(3)) to avoid the ArgumentOutOfRangeException.
Difference between Char.IsDigit() and Char.IsNumber() in C#