String.IsNullOrEmpty and Datarow.IsXnull

Question

How can I improve this code? What has made this long winded is the fact that I can't use string.IsNullOrEmpty on a data row and instead I have to use a dr.IsHOUSENUMBERNull method AND the string.IsNullOrEmpty to check if it is empty. Why is this? The column in the database is sometimes empty and sometimes NULL.

I'm sure this can be written better:

     If Not dr.IsHOUSENUMBERNull Then
           If Not String.IsNullOrEmpty(dr.HOUSENUMBER) Then
                sbAddress.AppendLine(dr.HOUSENUMBER + " " + dr.ADDRESS1)
           Else
                sbAddress.AppendLine(dr.ADDRESS1)
           End If   
     Else
           sbAddress.AppendLine(dr.ADDRESS1)      
     End If

Answer 1

You could do this, a bit shorter:

 If dr.IsHOUSENUMBERNull OrElse String.IsNullOrEmpty(dr.HOUSENUMBER) Then
       sbAddress.AppendLine(dr.ADDRESS1) 
 Else     
       sbAddress.AppendLine(dr.HOUSENUMBER + " " + dr.ADDRESS1)
 End If

Or if you want it more terse, though less readable in this case I think, use If():

sb.Address.AppendLine(If(r.IsHOUSENUMBERNull OrElse String.IsNullOrEmpty(dr.HOUSENUMBER), dr.ADDRESS1, dr.HOUSENUMBER + " " + dr.ADDRESS1))

Answer 2

I think only this much code is sufficient:

If Not String.IsNullOrEmpty(dr.HOUSENUMBER) Then 
   sbAddress.AppendLine(dr.HOUSENUMBER + " " + dr.ADDRESS1) 
Else 
   sbAddress.AppendLine(dr.ADDRESS1) 
End If 

Answer 3

There is a difference between the database's NULL and .NET's null (VB's Nothing when applied to reference types).

string.IsNullOrEmpty looks for .NET's null - not the database's NULL. So there is no need to check for null - only NULL/DBNull

If you store a database's NULL or .NET's null into a DataTable, you'll get back a DBNull.

AppendLine(object) call's object.ToString()

DBNull.Value.ToString() returns ""

Given all this information, your code could be simplified to:

sbAddress.Append(dr.HOUSENUMBER)
If Not dr.IsHOUSENUMBERNull AndAlso dr.HOUSENUMBER.Length <> 0 Then
    sbAddress.Append(" ")
End If
sbAddress.AppendLine(dr.ADDRESS1)