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Some ASP.NET Practical tips

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In an ASP.NET application, I faced some technical problems. In this article, I list them out and show the solutions that I found.  I hope it will be useful.

Problem:
After closing a pop-up window, the parent page should be refreshed automatically.

Solution:
In the parent page, call the method to pop-up a user defined page on any click event.
  var url = 'ManageFormsPopup.aspx';
 //Show the category window to manage categories
 var prefrence="height=400,width=500,status=yes,toolbar=no,menubar=no";
 window.open(url, null, prefrence);

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In the child page, trigger the onbeforeunload method.
window.onbeforeunload = RefreshParentPage;
//  ... 
function RefreshParentPage()
{
   // Refresh the parent page.
   window.opener.location.href = window.opener.location.href;
}

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Problem:
Inside an asp:panel control, RequiredFieldValidator is not working

Solution:
You can keep the RequiredFieldValidator outside of the panel.  This will not place the error message next to the text box. To place error message near to the text box, we have to validate explicitly using a Javascript function, like so:

function Validate()
{
  var categoryName = document.getElementById('<%=txtCategoryName.ClientID%>').value;

  if(categoryName.toString() == "")
  {
    document.getElementById('<%=lblValidate.ClientID%>').innerHTML = "Please enter Category Name";
    return false;
  }
  else {
    document.getElementById('<%=lblValidate.ClientID%>').innerHTML = "";
  }
  return true; 
}

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Problem:
While displaying a PDF file in a page, Reponse.End() throws an exception.

Solution:
Instead of Response.End() we could use Response.Close() to avoid the exception.

if (System.IO.File.Exists(FilePathVal))
{
    FileInfo fi = new FileInfo(FilePathVal); 
    long size = fi.Length;
    Response.AddHeader("Content-Length", size.ToString());
    Response.ContentType = "application/pdf";
    Response.BinaryWrite(File.ReadAllBytes(FilePathVal));
    Response.Flush();
    Response.Clear();
}

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Problem:
Before deleting a grid record, the user must be presented with a confirmation dialog.

Solution:
In the grid, use LinkButton template column.
<asp:TemplateColumn HeaderText="Delete">
<ItemTemplate>
<asp:LinkButton ID="lblDelete" CommandName="Delete" runat="server" Text="Delete"
 OnClientClick="javascript:return confirm('Are you sure you want to delete ?');"></asp:LinkButton>
</ItemTemplate>
</asp:TemplateColumn>

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Problem:
In a Grid link button (for example, clicking on Filename link button), a single click is not working sometimes.  Instead double clicking is working.

Solution:
The events should be bound to the link button while data bound itself using onItemDataBound event.
In client side:
<asp:DataGrid ID="grdResources" runat="server" AutoGenerateColumns="False"
 Width="100%" DataKeyField="ResID" OnItemDataBound="grdResources_ItemDataBound">

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In server side:
protected void grdResources_ItemDataBound(object sender, System.Web.UI.WebControls.DataGridItemEventArgs e)
{
Private const URL = "some file name";
   if (e.Item.ItemType == ListItemType.Item || e.Item.ItemType ==  ListItemType.AlternatingItem)
  {
    lnkSelect.Attributes.Add("onclick", "javascript:window.open('" + URL + "'); return true;");
  }
}

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Tip:
From a string array, you would like to check existence of a string quickly?
Create a List item for the string array and use Contains method of it.

private const string FormsAdmin = "FormsAdmin";
string[] Roles = cUser.Roles; 
List<string> RoleList = new List<string>(Roles);
if (RoleList.Contains(FormsAdmin))
{
  // Found the string.

}

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2 Comments
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Author Comment

by:Easwaran Paramasivam
Happy Reading! Happy coding!!
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LVL 1

Expert Comment

by:myaspnet
thank you
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