replace Null values - Cast from type 'DBNull' to type 'String' is not valid.

[Acuffdl]

I am starting to understand why the error "Cast from type 'DBNull' to type 'String' is not valid." is happening, but I am not sure how to determine WHICH line is failing ( I am in the middle of a DotNetNuke app and very new to .NET in general )..
But I can see the replace_Null function is failing.

the function:
Private Function replace_Null(ByVal myobj As Object) As String
If IsDBNull(myobj) Then
Return ""
Else
Return CStr(myobj)
End If
End Function

and the section of code that calls the function.
Is there a way like in classic asp to Response.Write = "HERE" ??
So I know where the error is occuring?

Public Function Load_Booth_Research(ByVal Trade_Show_ID As Integer, ByVal Company_ID As Integer) As Boolean
btn_update.Visible = True
Dim dr As SqlDataReader = leadsDB.get_market_company(Trade_Show_ID, Company_ID)
Load_Booth_Research = False
If dr.Read Then
'Top section
'**************************************************************
txt_research.Text = replace_Null(dr("researched_by"))
If CType(replace_Null(dr("front_end")), Boolean) = True Then
txt_front.Text = CStr(dr("front_end_booth")) 'crash here
Else
txt_front.Text = ""
End If

txtSalesperson.Text = replace_Null(dr("SMC_Salesperson"))
txtDistributorSalesperson.Text = replace_Null(dr("Dist_Salesperson"))

'Company Info
'**************************************************************
Booth_Research_ID = CInt(dr("Booth_Research_ID"))
txt_company.Text = replace_Null(dr("company_name"))
txt_Address.Text = replace_Null(dr("address1"))
txt_City.Text = replace_Null(dr("city"))
txt_Zip.Text = replace_Null(dr("zip"))
txt_Phone.Text = replace_Null(dr("phone"))
txt_WebAddress.Text = replace_Null(dr("website"))
txt_products.Text = replace_Null(dr("type_of_products"))
ck_on_display.Checked = CType(dr("tool_on_display"), Boolean)

'State
Try
drpState.Items.FindByText(replace_Null(dr("StateShort"))).Selected = True
Catch e As Exception

End Try

'Market Share
Try
drpMarketShare.Items.FindByValue(replace_Null(dr("Share_ID"))).Selected = True
Catch e As Exception

End Try

'Potential
Try
drp_potential.Items.FindByValue(replace_Null(dr("Potential_ID"))).Selected = True
Catch e As Exception

End Try

'Channel
Try
drpSalesChannel.Items.FindByValue(replace_Null(dr("channel_id"))).Selected = True
Catch e As Exception

End Try

'AS400
If Not IsDBNull(dr("isAS400")) Then
If CType(replace_Null(dr("isAS400")), Boolean) = True And CType(replace_Null(dr("isActive")), Boolean) = True Then
drpAS400.Items(1).Selected = True
ElseIf CType(replace_Null(dr("isAS400")), Boolean) = True Then
drpAS400.Items(2).Selected = True
Else
drpAS400.Items(3).Selected = True
End If
Else
drpAS400.Items(0).Selected = True
End If

'Company Type
Dim mydr As SqlDataReader = leadsDB.get_Type_by_Company(Company_ID)
While mydr.Read
Try
chkCompanyType.Items.FindByValue(CStr(mydr("Type_ID"))).Selected = True
Catch ex As Exception

End Try
End While

'Company Classification
mydr = leadsDB.get_Classification_by_Company(Company_ID)
While mydr.Read
Try
chkCompanyClass.Items.FindByValue(CStr(mydr("Classification_ID"))).Selected = True
Catch ex As Exception

End Try
End While


'Other
'*************************************************************
ck_pnuematic.Checked = CType(dr("pneumatic_equipment"), Boolean)

Try
drp_reason.Items.FindByText(replace_Null(dr("why_current_supplier"))).Selected = True
Catch ex As Exception
Dim sReason As String = replace_Null(dr("why_current_supplier"))
If sReason <> "" Then
drp_reason.Items.FindByText("Other").Selected = True
Else
drp_reason.Items.FindByValue("99").Selected = True
End If
txt_reason_other.Text = sReason
End Try

ck_catalog.Checked = CType(dr("want_catalog"), Boolean)
txt_catalog.Text = CType(replace_Null(dr("catalog_desc")), String)
ck_sales_person.Checked = CType(replace_bool_Null(dr("want_contact")), Boolean)

txt_comments.Text = replace_Null(dr("notes"))
Load_Booth_Research = True

Dim myparent As MarketResearch = CType(Me.Parent, MarketResearch)
Load_Product_Competitor_Tables(CInt(myparent.Trade_Show_ID), Company_ID)
Load_Contacts(Company_ID)
End If

dr.Close()
End Function

[timeshifter]

Instead of using IsDBNull, try this:

If String.IsNullOrEmpty(myStr) Then

[Acuffdl]

HI there,

The specific crash is occuring on the db column front_end_booth (it has nulls):

If CType(replace_Null(dr("front_end")), Boolean) = True Then
txt_front.Text = CStr(dr("front_end_booth")) 'crash here
Else
txt_front.Text = ""
End If

So the application is saying "Hey wait!!, I cant convert a NULL to a String!!" ??

[Acuffdl]

Hi there.
I tried changing the replace_Null function to:

If String.IsNullOrEmpty(myobj) Then..

But I am getting an error in the source:
'IsNullOrEmpty is not a member of String'

[techgnome]

Acuffdl - what version of VB are you using?

=tg

[Acuffdl]

This is an old DotNetNuke version 2.1 circa 2001?

And Visual Basic 2003.net is kicking in as the IDE instead of my newly prefered VS 2005...