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ASP.net error

Posted on 2011-03-13
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Last Modified: 2012-05-11
Hi

I am getting the following error on the code shown below in ASP.net
Warning	1	Function 'ExcelConnection' doesn't return a value on all code paths. A null reference exception could occur at run time when the result is used.	C:\Users\User\Documents\Visual Studio 2010\Projects\Green Calendar\Green Calendar\Upload.aspx.vb	63	5	Green Calendar

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Question by:Murray Brown
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7 Comments
 
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Expert Comment

by:wdfdo1986
ID: 35121408
post the upload.aspx back end code or excel connection function at least
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Expert Comment

by:Rajkumar Gs
ID: 35121453
If there is any 'If' condition OR 'switch' something like that you need to return the value in all conditions
In other words , the function need to return value in all of its condition. Surely in some condition it is missing - please check

Raj
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LVL 6

Expert Comment

by:Ramone_Hamilton
ID: 35121725
In your ExcelConnection function you are not returning a valid value for the functions end points.  If the function is boolean you need to make sure you return a true or false, an integer returns an integer etc.
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Author Comment

by:Murray Brown
ID: 35121895
Sorry. Thought I had posted the code. Here iy is:
Imports System.Data.OleDb

Public Class WebForm1


    Inherits System.Web.UI.Page

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load

    End Sub


    Protected Sub ButtonUpload_Click(ByVal sender As Object, ByVal e As EventArgs) Handles ButtonUpload.Click
        Try
            PanelUpload.Visible = True
            PanelView.Visible = False
            PanelImport.Visible = False
        Catch ex As Exception
            MsgBox(Err.Description)
        End Try

    End Sub

    Protected Sub ButtonUploadFile_Click(ByVal sender As Object, ByVal e As EventArgs) Handles ButtonUploadFile.Click
        If FileUploadExcel.HasFile Then
            Try
                ' alter path for your project
                FileUploadExcel.SaveAs(Server.MapPath("~/ExcelImport.xls"))
                LabelUpload.Text = "Upload File Name: " & _
                    FileUploadExcel.PostedFile.FileName & "<br>" & _
                    "Type: " & _
                    FileUploadExcel.PostedFile.ContentType & _
                    " File Size: " & _
                    FileUploadExcel.PostedFile.ContentLength & " kb<br>"
            Catch ex As Exception
                LabelUpload.Text = "Error: " & ex.Message.ToString
            End Try
        Else
            LabelUpload.Text = "Please select a file to upload."
        End If

    End Sub
    Protected Function ExcelConnection() As OleDbCommand
        Try
            ' Connect to the Excel Spreadsheet
            Dim xConnStr As String = "Provider=Microsoft.Jet.OLEDB.4.0;" & _
                  "Data Source=" & Server.MapPath("ExcelImport.xls") & ";" & _
                  "Extended Properties=Excel 8.0;"

            ' create your excel connection object using the connection string
            Dim objXConn As New OleDbConnection(xConnStr)
            objXConn.Open()
            ' use a SQL Select command to retrieve the data from the Excel Spreadsheet
            ' the "table name" is the name of the worksheet within the spreadsheet
            ' in this case, the worksheet name is "Members" and is expressed as: [Members$]
            Dim objCommand As New OleDbCommand("SELECT * FROM [Members$]", objXConn)
            Return objCommand

        Catch ex As Exception
            MsgBox(Err.Description)
        End Try

    End Function



    Protected Sub ButtonView_Click(ByVal sender As Object, ByVal e As EventArgs) Handles ButtonView.Click

        Try
            'The ButtonView_Click event handler starts by hiding the PanelUpload and PanelImport Panels,
            ' while showing the PanelView interface (which is where the GridView is located).
            PanelUpload.Visible = False
            PanelView.Visible = True
            PanelImport.Visible = False
            'Next, a new OleDbDataAdapter object is created and its SelectCommand is assigned the OleDbCommand object returned by the ExcelConnection function.
            ' Create a new Adapter
            Dim objDataAdapter As New OleDbDataAdapter()

            ' retrieve the Select command for the Spreadsheet
            objDataAdapter.SelectCommand = ExcelConnection()
            'The purpose of this OleDbDataAdapter object is to populate a DataSet with the contents of the Excel query; this DataSet is then bound to the GridView.
            ' Create a DataSet
            Dim objDataSet As New DataSet()

            ' Populate the DataSet with the spreadsheet worksheet data
            objDataAdapter.Fill(objDataSet)

            ' Bind the data to the GridView
            GridViewExcel.DataSource = objDataSet.Tables(0).DefaultView
            GridViewExcel.DataBind()
        Catch ex As Exception

            MsgBox(Err.Description)

        End Try

    End Sub



End Class
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LVL 23

Accepted Solution

by:
Rajkumar Gs earned 500 total points
ID: 35122117
try return null in the function's try catch

Protected Function ExcelConnection() As OleDbCommand
.....................
Catch ex As Exception
            MsgBox(Err.Description)
            return null
End Try
End Function

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Author Closing Comment

by:Murray Brown
ID: 35122279
Thanks
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LVL 23

Expert Comment

by:Rajkumar Gs
ID: 35122338
my pleasure
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