Conversion from string “DESC” to type 'Double' is not valid.

[dwinn86]

I am developing a site in ASP.Net and VB.Net that will enable users to sort data in a GridView in Ascending or Descending order.

The records are coming from an SQL Server Express database.

I go to click on a column heading to sort the data and I get the following error:

'Conversion from string "DESC" to type 'Double' is not valid.'

Below is the code I am using for the sorting:

Protected Sub Button3_Click(ByVal sender As Object, ByVal e As EventArgs) Handles Button3.Click

Dim sqlConn As New SqlConnection
Dim sqlCmd As New SqlClient.SqlCommand
Dim sqlReader As SqlDataReader

'If no values are supplied in the textbox, throw an error message.
If TextBox2.Text = "" Then
MsgBox("A centre code needs to be provided...")
End If

If TextBox2.Text <> "" Then

'Telling the system the location of the database.
sqlConn.ConnectionString = "server=servername;Initial Catalog=dbName;Trusted_Connection=yes"

'Here we are opening the connection to the database.
sqlConn.Open()

'This is to say that sqlCmd is a stored procedure.
sqlCmd.CommandType = System.Data.CommandType.StoredProcedure

'This is creating the command to execute the stored procedure based on the information given in the connection string.
sqlCmd = sqlConn.CreateCommand

'The command is triggered to execute the stored procedure which grabs all information for the specific centre.
sqlCmd.CommandText = "exec ProcedureName'" & TextBox2.Text & "' "

'This will read the rows in the database.
sqlReader = sqlCmd.ExecuteReader()

GridView2.Columns.Clear() 'If there are rows of data that match are criteria
If (sqlReader.HasRows) Then

'The rows of data are grabbed for the specific centre from the database using the data reader.
GridView2.DataSource = sqlReader
GridView2.DataBind()
GridView2.Columns.Clear()
Else
MsgBox("The centre code provided does not exist...")
End If

'This is closing the connection to the database once we have finished with it.
sqlConn.Close()

'This is to clear the list of items out of the GridView box.

End If

End Sub

Property GridViewSortDirection() As String
Get
If IsNothing(ViewState.Item("GridViewSortDirection")) Then
Return "desc"
End If
Return ViewState.Item("GridViewSortDirection")
End Get

Set(ByVal Value As String)
ViewState.Item("GridViewSortDirection") = Value
End Set

End Property

Function GetSortDirection() As String

Dim GridViewSortDirectionNew As String

Select Case GridViewSortDirection

Case "DESC"
GridViewSortDirectionNew = "ASC"

Case "ASC"
GridViewSortDirectionNew = "DESC"

Case Else
GridViewSortDirectionNew = "DESC"

End Select
GridViewSortDirection = GridViewSortDirectionNew

Return GridViewSortDirectionNew

End Function

Protected Sub GridView_Sorting1(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.GridViewSortEventArgs) Handles GridView2.Sorting

Dim myPageIndex As Integer = GridView2.PageIndex
Dim mySortdirection As String = GetSortDirection()
Dim sortExpression = e.SortExpression
Dim dv As New DataView()


If (GridViewSortDirection = SortDirection.Ascending) Then

GridViewSortDirection = SortDirection.Descending
'SortGridView(sortExpression, "DESCENDING")
Else
GridViewSortDirection = SortDirection.Ascending

End If


'dv.Table = GridView2.DataSource

' dv.Sort = e.SortExpression & " " & mySortdirection
' GridView2.DataSource = dv
'
' GridView2.DataBind()
'
' GridView2.PageIndex = myPageIndex

End Sub

'Protected Sub SortGridView(string sortExpression,string direction)

'DataTable dt = GetData().Tables[0]

' DataView(GridView2 = New DataView(GridView2))
' GridView2.Sort = sortExpression + Direction
'
' GridView1.DataSource = GridView2
' GridView1.DataBind()
'
' End Sub

My GridView looks like:

 

< asp:GridView ID="GridView2" runat="server" Height="143px" AllowSorting="true" OnSorting="GridView_Sorting1"

How can I get past this problem?

All help and advice will be greatly appreciated.

Many thanks,

Dan

[keystone_paul]

Can you indicate which line of code you're getting the error on.

[dwinn86]

Hello,

I get the error on the following line:

If (GridViewSortDirection = SortDirection.Ascending) Then

Thanks,

Dan

[Grimfort]

You are trying to compare a string against an enum, its a completely different type!

You need to either change your GridViewSortDirection property into the same type, or compare it as text instead.

Property GridViewSortDirection() As SortDirection

[dwinn86]

I have set it so that it is now the same type, and when I go to click on the column to sort it I now get an error pointing to:

Case "desc"

With the error now saying:

Conversion from string "desc" to type 'Integer' is not valid.

Any help please?

Thanks,

Dan

[Grimfort]

You have exactly the same problem. You have converted your string to the type, but are still testing it as a string!

Select Case GridViewSortDirection

Case SortDirection.Ascending

[dwinn86]

Hey,

I have now changed them so I am not testing the string anymore:

Property GridViewSortDirection() As SortDirection
            Get
                If IsNothing(ViewState.Item("GridViewSortDirection")) Then
                    Return SortDirection.Descending
                End If
                Return ViewState.Item("GridViewSortDirection")
            End Get
 
            Set(ByVal Value As SortDirection)
                ViewState.Item("GridViewSortDirection") = Value
            End Set
 
        End Property
   
        
        
        Function GetSortDirection() As SortDirection
  
            Dim GridViewSortDirectionNew As SortDirection
 
            Select Case GridViewSortDirection
 
                Case SortDirection.Descending
                    GridViewSortDirectionNew = SortDirection.Ascending
                    
                Case SortDirection.Ascending
                    GridViewSortDirectionNew = SortDirection.Descending
                    
                Case Else
                    GridViewSortDirectionNew = SortDirection.Descending
                    
            End Select
            GridViewSortDirection = GridViewSortDirectionNew
            
            Return GridViewSortDirectionNew
            
        End Function
        

  
        Protected Sub GridView_Sorting1(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.GridViewSortEventArgs) Handles GridView2.Sorting
            
            'Dim myPageIndex As Integer = GridView2.PageIndex
            Dim mySortdirection As SortDirection = GetSortDirection()
            'Dim sortExpression = e.SortExpression
            'Dim dv As New DataView()
            
            
            If (GridViewSortDirection = SortDirection.Ascending) Then
                GridViewSortDirection = SortDirection.Descending
            Else
                GridViewSortDirection = SortDirection.Ascending
            End If

        End Sub

However, when I click on to a column, nothing actually happens now.

Any reason for this?

Thanks,

Dan

[Grimfort]

2 reasons.

1.

Dim mySortdirection As SortDirection = GetSortDirection()  <<< You already change the direction INSIDE that sub
            'Dim sortExpression = e.SortExpression
            'Dim dv As New DataView()
                        
            If (GridViewSortDirection = SortDirection.Ascending) Then  <<< And you are reversing it AGAIN here
                GridViewSortDirection = SortDirection.Descending
            Else
                GridViewSortDirection = SortDirection.Ascending
            End If

2. You are not actually doing anything with the property...

[dwinn86]

Ok then, I get that what I am doing in GridView_Sorting1 I have already done in GetSortDirection.

How do I go about getting the data to sort when I click on the column header??

Thanks for your help so far.

Dan

[Grimfort]

I think I can guess that you picked up this code from here. I have never used it before.
The eventargs has a parameter you can change to set the sortorder, surely you just change that?

e.SortExpression = GetSortDirection

[dwinn86]

Hi Grimfort,

Can you explain a bit more please?

I am starting to understand, but need a bit more details.

Would I do:

If e.SortExpression = SortDirection.Ascending Then
    GridViewSortDirection = SortDirection.Descending
Else
    GridViewSortDirection = SortDirection.Ascending
End If

Is that along the right lines?

If it isnt, would you mind advising on the what the right lines would be?

Thanks,

Dan

[Grimfort]

Look at the link I posted to here. I have not used this before. The example shows a string version in order to create a sort expression, not the type (which you changed it to after my comment, as I had no idea why you were using it!). Simple answer is to remove what you have done, and use the code from the sample.