AJAX – Export to Excel / Word

If you are using Update Panel and try to Export gridview contents to EXCEL or Word, your asp.net page will throw nasty error. “Sys.WebForms.PageRequestManagerParserErrorException”

Its because AJAX & Response.write don’t go together.  By calling Response.Write() directly you are bypassing the normal rendering mechanism of ASP.NET controls. The bits you write are going straight out to the client without further processing (well, mostly…). This means that UpdatePanel can’t encode the data in its special format.

There are couple of ways to solve this problem.

1. Place the Export Button outside of Update Panel.

2. By Pass the Export Button using <Triggers>

 </ContentTemplate>
        <Triggers>
            <asp:PostBackTrigger ControlID=”cmdExport” />
        </Triggers>
</asp:UpdatePanel>
if your Export button is part of UserControl then specify usercontrolid:buttonid

 </ContentTemplate>
        <Triggers>
            <asp:PostBackTrigger ControlID=”uscSelCtl:cmdExport” />
        </Triggers>
    </asp:UpdatePanel>

More Reading…

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Asp.Net Filter Datatable by Column

Filter Datatable by Rows

If you need to get subset of a big dataset into datatable Rowwise …

Dim dtEmp as DataTable
Dim dsEmployee as New DataSet

dsEmployee = someobject.getdata()  'dataset can be populated in many ways which is not explained here.

Dim sExpr as String
Dim drRows() as DataRow, drSingleRow as DataRow

sExpr = "EmpID > 100"  'Condition

drRows = dsEmployee.Tables(0).Select(sExpr)

'If you need to add Sort Order it can be added to sExpr

Dim sSortOrder as String
sSortOrder = "EmpName DESC"
drRows = dsEmployee.Tables(0).Select(sExpr,sSortOrder)

For Each drSingleRow in drRows
 dtEmp.ImportRow(drRows)
Next

' Datatable dtEmp has filtered records

Filter Datatable by Column

If you need to get subset of big dataset into datatable columnwise…

Dim dtEmp as DataTable
Dim dsEmployee as New DataSet

dsEmployoee = someobject.getdata()  'dataset can be populated in many ways which is not explained here.

'This copies the structure and data

dtEmp = dsEmployee.Tables(0).Copy

dtEmp.Columns.Remove("Unwanted Column 1")
dtEmp.Columns.Remove("Unwanted Column 2")
dtEmp.Columns.Remove("Unwanted Column 3")

Prevent Session Timeout in Asp.net

Prevent Session Timeout in Asp.net [VB]

ASP.Net 2.0 [VB]

Inspired by this article from Code Project. [Thanks Ach1lles ]

---

I slightly modified few things to work for VB and VS2005 environment. The code works perfect and I’m very happy with it.First I created a Module file and created this function.

Public Function KeepAlive() As String

        Dim int_MilliSecondsTimeOut As Integer = (HttpContext.Current.Session.Timeout * 60000) - 30000
        Dim sScript As New StringBuilder
        sScript.Append("<script type='text/javascript'>" & vbNewLine)
        'Number Of Reconnects
        sScript.Append("var count=0;" & vbNewLine)
        'Maximum reconnects Setting
        sScript.Append("var max = 6;" & vbNewLine)
        sScript.Append("function Reconnect(){" & vbNewLine)
        sScript.Append("count++;" & vbNewLine)
        sScript.Append("var d = new Date();" & vbNewLine)
        sScript.Append("var curr_hour = d.getHours();" & vbNewLine)
        sScript.Append("var curr_min = d.getMinutes();" & vbNewLine)
        sScript.Append("if (count < max){" & vbNewLine)
        sScript.Append("window.status = 'Refreshed ' + count.toString() + ' time(s) &#91;' + curr_hour + ':' + curr_min + '&#93;';" & vbNewLine)
        sScript.Append("var img = new Image(1,1);" & vbNewLine)
        sScript.Append("img.src = 'http://localhost/myapp/reconnect.aspx';" & vbNewLine)

        sScript.Append("}" & vbNewLine)
        sScript.Append("}" & vbNewLine)
        sScript.Append("window.setInterval('Reconnect()',")
        sScript.Append(int_MilliSecondsTimeOut.ToString() & "); //Set to length required" & vbNewLine)
        sScript.Append("</script>")

        KeepAlive = sScript.ToString
End Function

All this code does is, build a simple javascript function and its called from server side.The works like this,- Gets the current session timeout duration.
– Subtract 30 seconds from it and assign it to MilliSecondsTimeOut variable
– Create a Reconnect() javascript function
– Create a global variable with max value 6
– Get current hour and Min [just for displaying the last refresh time]
– Verify whether count is less than max value (ie 6)
– If so, change the window status with Text
– Create a dummy image and set reconnect.aspx url as its source [this way a call is made to server and it wont session timeout]Create a timer using window.setInterval and assign the MilliSecondsTimeOut value.
[this way this function is called 30 seconds before session timeout]Tha max value (6) can be set to any number. If its 6 then this session timeout is avoided 5 times.

Default session timeout is 20min. 20 * 5 = 100 mins. Which is good for non-secure page.

Then

On the pages where I want to prevent Session Timeout I entered this line.

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
Try
  'dont forget to add this line 
  Page.ClientScript.RegisterClientScriptBlock(Me.GetType, "reconn key", KeepAlive())
 
 If Not Page.IsPostBack Then
 ---
 ---
 ---
 End If

Catch eX as Exception
 '----
End Try
End Sub

Created reconnect.aspx in Visual Studio and deleted the .vb and .designer.vb files.This is the final version of reconnect.aspx

<%@ Page Language="vb" AutoEventWireup="false"%>
<%@ OutputCache Location="None" VaryByParam="None" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "<a href="http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd" mce_href="http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd</a>">
<html xmlns="<a href="http://www.w3.org/1999/xhtml" mce_href="http://www.w3.org/1999/xhtml">http://www.w3.org/1999/xhtml</a>" >
</html>

Note : When you compile the project sometimes, VS2005 complains reconnect.aspx is not in right format.
So I EXCLUDED this file from my project. Now VS 2005 will compile without complaining and the logic will also work.- Happy Programming

Copy Datatable from one Dataset to another Dataset

 Copying a datatable from one dataset  to another was not that straightforward as I thought.

Dim dsSource As New DataSet
Dim dsDestination As New DataSet

'Your way to get data from XML or DB.
dsSource = object.getdata()

dsDestination = object.getmoredata()

'This is important, without this it will result in error
'when you try to copy the datatable from one dataset to another

dsSource.Tables(0).TableName = "NewTableName"

dsDestination.Tables.Add(dsSource.Tables(0).Copy)

dsDestination.Tables(0).Tablename = "SomeTable"
dsDestination.Tables(1).Tablename = "NewTableName"   'The one we copied from other Dataset

Note 1 : When you are using more than one datatable in a dataset it is advisable you name the datatables.

Note 2 : These kinds of scenarios arise, when you are trying to establish Relation between datatables in a dataset.

(Cascading master – detail relation)
 

Creating dynamic, fancy EmptyDataText for GridView

Gridview has capability to display “default” messages when “No data” exists during binding.

Standard Way in .aspx

<asp:GridView ID=”gvControl” runat=”server” AutoGenerateColumns=”False” GridLines=”None” CellPadding=”0″ CellSpacing=”0″ OnRowDataBound=”gvCategories_RowDataBound” BackColor=”#dddddd” ShowHeader=”false” EmptyDataText=”<BR> No data exists <BR><BR>“>
….
…..
</asp:GridView>

Fancy Way (.vb or .cs)

You can make it fancy & dynamic by doing it in code behind.

Create fancy texts using WordArt (MS Word) and copy it to Image Editor (Paint.net, gimp, Paint) and save it as JPG.

 
gvControl.EmptyDataText = "<img src='~/images/NoData.jpg' border='0'>"
gvControl.EmptyDataRowStyle.HorizontalAlign = HorizontalAlign.Center
gvControl.databind

Note: When you use emptydatatext in codebehind donot forget to use databind.

‘The invoked member is not supported in a dynamic module.’

Error ‘The invoked member is not supported in a dynamic module.’ while generating exception string

While Using ASPUnhandledException.dll for exception handling, I received this error via email.

This error message was not at all helpful in production environment. 

On careful debugging I found out that my Stored Proc failed.

Instead of giving the reason for Stored Proc failure it gave this obscure message. If  someone knows why it gives this message it will be helpful.

(reason my sp failed was because I was calling a non-existing user defined function)

Locking Cell and Changing Cell Style UltraWebGrid

Refer this article for Column Locking / Freezing in Infragistics Ultra WebGrid

If you need to change background color for a  frozen columns then ..
backcolor property must be changed first then cells have to be locked.

  e.Layout.Bands(0).Columns(0).CellStyle.BackColor = Drawing.Color.Beige
  e.Layout.Bands(0).Columns(0).Header.Fixed = True

and in InitializeLayout of ultraWebgrid

Private Sub ultrawebgrid_InitializeLayout(ByVal sender As Object, ByVal e As Infragistics.WebUI.UltraWebGrid.LayoutEventArgs) Handles uwgCategory.InitializeLayout

e.Layout.UseFixedHeaders = True

End Sub 

 

 

 

Comment on Server Side Asp.Net

Inspired by ASP.NET 2.0 Server Side Comments

If you want to comment a particular column in GridView, HTML commenting approach wont work.

You have to use

<%--

--%>

example:

<asp:GridView ID="gvSample" runat="server" AutoGenerateColumns="False"
GridLines="None" CellPadding="0" CellSpacing="0">
<Columns>
<asp:BoundField DataField="Column1" ItemStyle-Width="25px" />
<asp:BoundField DataField="Column2" ItemStyle-Width="15px" />
<asp:BoundField DataField="Column3" ItemStyle-Width="15px" />

<%-- Commented Column --%>
&lt;%-- <asp:BoundField DataField="Column4" ItemStyle-Width="15px" />--%>

</Columns>
</asp:GridView>

Call Javascript Function inside asp:Hyperlink Control

If you ever want to call a javascript function (with or without  parameter) from a server side hyperlink control here it is..

Step 1 :

declare your javascript function between

Step 2:

<asp:HyperLink ID=”hypCate” runat=”server”

NavigateUrl='<%# “javascript:showPopUp(” & DataBinder.Eval(Container.DataItem, “ID”) & “);” %>’

Text='<%#DataBinder.Eval(Container.DataItem, “Name”)%>’ />

Carefully follow the single and double quotes for NavigateUrl attribute.

Needless to say showPopUp is the name of Javascript Function.

It displays the NAME as hyperlink. Clicking that calls javascript showPopUp.

Column Locking / Freezing in Infragistics Ultra WebGrid

(NetAdvantage for ASP.NET)

If you want to freeze first few columns like EXCEL and horizontally scroll rest of the columns in Ultra WebGrid here you go…

Event :

UltraWebGrid1_InitializeLayout(object sender, Infragistics.WebUI.UltraWebGrid.LayoutEventArgs e)

VB Code :

e.Layout.UseFixedHeaders = true
e.Layout.Bands(0).Columns(1).Header.Fixed = true
e.Layout.Bands(0).Columns(2).Header.Fixed = true

Above code freezes the  two columns (second,third) in Grid.

C# Code

protected void UltraWebGrid1_InitializeLayout(object sender, Infragistics.WebUI.UltraWebGrid.LayoutEventArgs e)
{

e.Layout.UseFixedHeaders = true;
e.Layout.Bands[0].Columns[1].Header.Fixed = true;
e.Layout.Bands[0].Columns[2].Header.Fixed = true;

}

Gridview : Empty First Row / Asp.net 2.0

If you using Gridview control and your Grid doesnt have HEADER information then make sure you turn off the “ShowHeader” property for that Gridview or else you will notice a blank line on top of the grid.  If you are

If you do viewsource you will notice this mystery line <tr><th></th</tr> as first line of grid table.