IsDBNull problem

IsDBNull problem

• T-W

  I only suggested testing for Nothing in case you object had nothing to do with databases.

  Anyhow, you still didn't answer my question.

  
  

• bennett_chen

  Isdbnull Method
  http://msdn2.microsoft.com/en-us/library/tckcces5.aspx

  Returns a Boolean value indicating whether an expression evaluates to the System.DBNull class.

  DBNull Class 
  Represents a nonexistent value. This class cannot be inherited
  DBnull is in fact system.dbnull and is a class,   Null (Nothing) in vb is not the same as dbnull.   So you need to be careful that you are using the right one otherwise it may provide strange results.

   

  A search on the forums on isdbnull will detail it and potential pitfalls that can cause confusing results.   I'd suggest having a look at these and see if either of these actually helps you out.

  http://forums.microsoft.com/MSDN/ShowPost.aspx PostID=555922&SiteID=1

   http://forums.microsoft.com/MSDN/ShowPost.aspx PostID=129341&SiteID=1

   

  Which line specifically is throwing the exception  

  and what value do you think should be in the database for this item

   

  
  

• Modez

  Yes and it wont let me, this is the error

  For columns not defined as System.String, the only valid value is (Throw exception).

  This is a date field.

  Is there a work around for this.

  Davids Learning

  
  

• madrikh

  Are you saying that IsDBNull is returing true or that an error is being generated

  If its the later then post the exact error message.

  What sort of object is EDFRow.EStart

  Should you perhaps be testing if it's Nothing

  
  

• bchu

  You are assuming that this line actually returns a value.

  EDFRow = ST102ADataSet.EDF.FindByEName(Me.ENameListBox.SelectedValue.ToString)

   

  Test EDFRow as follows:

  If EDFRow IsNot Nothing Then

       'do your other code here

  Else

       'do your else code here

  End if

  
  

• Steve Hempen

  It is an exeption error

  It says that the field I am refering to is DBNull

  It stops my code from executing to give me that error

  Sorry

  Davids Learning

  
  

• TomJ72

  Didnt post all of my code, sorry

  Dim EDFRow As ST102ADataSet.EDFRow

  If Me.ENameListBox.SelectedItems.Count = 1 Then

  EDFRow = ST102ADataSet.EDF.FindByEName(Me.ENameListBox.SelectedValue.ToString)

  If IsDBNull(EDFRow.EStart) Then

  Me.EStartDateTimePicker.Checked = False

  Else

  Me.EStartDateTimePicker.Checked = True

  End If

  EDFRow.EStart is a field in a table that is a smalldate

  IsNothing didnt work

  IsNothing I thought would not work on a null field in a table, I thought IsNothing refers to a control only

  I am trying to find out if the fields value for the record is null, then if it is , get a date picker to not show a date until the field has data in it.

  Davids Learning

  
  

• laboremus

  If (EDFRow.isEStartNull = True) Then

  Me.EStartDateTimePicker.Checked = False

  Else

  Me.EStartDateTimePicker.Checked = True

  End If

  
  
  
  isEStartNull Method is provided by default for typed datasets. :)
  
  
  

• Krela

  This is the exact error

  The value for column 'EStart' in table 'EDF' is DBNull.

  <System.Diagnostics.DebuggerNonUserCodeAttribute()> _

  Public Property EStart() As Date

  Get

  Try

  Return CType(Me(Me.tableEDF.EStartColumn),Date)

  Catch e As System.InvalidCastException

  Throw New System.Data.StrongTypingException("The value for column 'EStart' in table 'EDF' is DBNull.", e) <<This Line

  End Try

  End Get

  Set

  Me(Me.tableEDF.EStartColumn) = value

  End Set

  End Property

  There is nothing in the field in the database - it is a field that will hold a future date.

  Davids Learning

  
  

• auto

  Did you check the DataSet Designer that the Column is not set to ThrowException on DBNull

  
  
• IsDBNull problem