CHECK FOR NULL IN VB

[DonJohnson]

I am trying to identify a NULL value in a string field and assign a value. 

IsNull = True is causing an error. 

Any other suggestions?

[NeilClemmons]

The following is VB.NET.

    Public Shared Function GetStringValue(ByVal value As Object) As String
        If value Is DBNull.Value Then
            Return String.Empty
        Else
            Return Convert.ToString(value)
        End If
    End Function

[DonJohnson]

I am using ModelBuilder and have the following:

Dim ROAD as String
ROAD = [ROAD_NAME]

if isNull(ROAD) = True then
ROAD = "NONE"
End If

[JamesCrandall]

Not familiar with ModelBuilder, but the VB.NET function to check for null values is the IsDBNull function.  Maybe something like this? (although I am not sure about getting/setting your "[ROAD_NAME]" value):

Dim ROAD As String
If Not IsDBNull([ROAD_NAME]) Then
  ROAD = [ROAD_NAME]
Else
  ROAD = "NONE"
End If

I am using ModelBuilder and have the following:

Dim ROAD as String
ROAD = [ROAD_NAME]

if isNull(ROAD) = True then
ROAD = "NONE"
End If

[JohnHauck]

Please use the following:

Dim ROAD as String
If IsNull( [ROAD_NAME]) Then
ROAD = "NONE"
Else
ROAD = [ROAD_NAME]
End If

[EllenTejan]

Thank you don

I imbeded

isNull(ROAD) = True

into  my expression and it worked for me.

Ellen