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Object reference not set to an instance of an object.

I am getting the following error from the below procedure at the high lighted line :

"Object reference not set to an instance of an object."

error line : _CopyWorkflowItemID = command.ExecuteScalar().ToString()

Function:

 Function GetWorkFlowItemId(ByVal StID As String) As String

        Dim connection As SqlConnection = Nothing

        Try
            connection = New SqlConnection(strConnection)
            Dim command As New SqlCommand(Me.GetSPX("spx_StCopyForm_SELECT"), connection)
            command.CommandType = CommandType.StoredProcedure

            Dim StIDParam As SqlParameter = New SqlParameter("@StID", SqlDbType.VarChar, 50)
            StIDParam.Value = StID
            command.Parameters.Add(StIDParam)

            Dim StSetParam As SqlParameter = New SqlParameter("@StSet", SqlDbType.Int)
            StSetParam.Value = _StSet
            command.Parameters.Add(StSetParam)

            Dim workflowIDParam As SqlParameter = New SqlParameter("@WorkflowID", SqlDbType.VarChar, 50)
            workflowIDParam.Value = _WorkflowID
            command.Parameters.Add(workflowIDParam)
            connection.Open()
            _CopyWorkflowItemID = command.ExecuteScalar().ToString()
            If Not String.IsNullOrEmpty(_CopyWorkflowItemID) Then
                If _CopyWorkflowItemID <> _WorkflowItemID Then
                    Return _CopyWorkflowItemID
                End If
            End If
        Finally
            If Not connection Is Nothing Then connection.Close() : connection.Dispose()
        End Try

        Return _WorkflowItemID
    End Function

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Please help me !

PeteEngineer

ASKER

i think its coused because of no rows in the return of store proc

AndyAinscow

Instead of
_CopyWorkflowItemID = command.ExecuteScalar().ToString()

does this work
Object obj = command.ExecuteScalar()
if not isnull(obj) then _CopyWorkflowItemID = obj.ToString()

Rouchie

Check that spx_StCopyForm_SELECT always returns a value regardless of whether data is affected or not

PeteEngineer

ASKER

I found no data in table ... and nor inserting any thing into this table anywhere in the application.

So can we do an error handling here .. ?

How to do that ...

can we do by checking null of that object using a if statement

if so , what we can write in the else statement to handle this ?

Please write the code by editing my previous function posted in question.

SOLUTION

Rouchie

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PeteEngineer

ASKER

its just a select command :

ALTER PROCEDURE [dbo].[spx_StDetailCopyForm_SELECT](
@StyleID uniqueidentifier,
@StyleSet int,
@WorkflowID uniqueidentifier)

AS 
BEGIN
	SELECT	 WorkFlowItemId 
	FROM	  pStDetailForm 
	WHERE	 StyleID = @StyleID AND 
			StyleSet = @StyleSet AND 
			WorkflowID = @WorkflowID
END

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AndyAinscow

>>can we do by checking null of that object using a if statement
See my first comment.
I'm not a VB specialist but basically split that line into two lines of code - so you can check if the command.ExecuteScalar is actually returning an object or null.

PeteEngineer

ASKER

yes it is null ,

but i want to know what sepecally i need to handle ..what to put in else statement if it is not null

SOLUTION

AndyAinscow

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ASKER CERTIFIED SOLUTION

Rouchie

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