Contents tagged with VB.NET
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Update to my LINQ to SQL performance in VB.NET saga
Hello,
If you have read my posts before where I was complaining about VB generated sub optimal SQL when using nullable columns in your where clauses, I came to the conclusion I was being silly and not using .Value on those nullable fields in my queries.
I stumbled across this post today:
http://blogs.msdn.com/vbteam/archive/2008/03/28/linq-to-sql-and-linq-to-entities-performance-improvements-tim-ng.aspx
Looks like it was an issue in the end and not me being totally stupid :). -
Output Cache With Usercontrol on Masterpage and Multiple VaryByCustom
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Different SQL between VB.NET and C# LINQ to SQL SOLVED!!
Hi All,
Following my previous post I have solved this issue. Somehow accidently I discovered that if the field has allow nulls set on it VB.NET will add the Where Coalesce in your query hence in my case slowing it down dramatically. It seems that C# does not do this. So finally I have my VB.NET sql comming out exactly the same as in C# simply by turning off allow nulls on my database column... Still seems like odd behaivour to me but for now it all works fine.
Thanks
Stefan -
UserControl OutputCache and VaryByParam not working with postback!!
Don't know if anyone has come across this before. But if you have a usercontrol that uses VaryByParam and you have it on a page and do a postback you will get the wrong cache item. Use the below test bed to see what I mean, this is following to my post for help on the asp.net forums, I then found this post which showed me it is an issue, following this I think I came up with a solution. That is to add a hidden field to my page with the name MenuID and populate that. Now on postback it seems to work fine, as VaryByParam="MenuID" seems to read the form var MenuID and gets the correct value hence fixing caching.
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Fully Accessible And SEO Friendly Ajax Paging Using DataPager
Hey All,
Working on my current project I implemented paging using a listview and a datapager. I then decided it would be much nicer to use AJAX for my paging so wrapped all this up in an updatepanel. Next step was the issue when you would goto a page, select a product and hit the browser back button you would get the first page not the page you were last on. To fix this I simply implemented the ASP.NET AJAX Futures History control which allowed me to save my current page and restore this at a later time.
Perfect I thought until I started thinking about SEO, now my product catalogue was dead to a search engine as it would only see the first page and not be able to do any further paging. To fix this I went about creating a SEO friendly linkbutton control (I have blogged about this a while back but this is the first time I used it in real life). Basically what the SEO Friendly linkbutton does is render a normal navigateURL and the postback as an onclick. This way with Javascript turned on you get a postback but without you have a normal URL, in my case I am passing the page # in my url like so: http://site.com/catalogue/page-XX/Whatever.aspx, I am using URL Rewriter.NET for my URL rewriting so making a nice URL for this was as simple as adding a new rule into my web.config.
Firstly here is my custom SEOLinkButton control (Its in VB.NET as is my current project, I have a C# version too but will just post the VB.NET version unless requested):
Public Class SEOLinkButton
Inherits LinkButton
#Region "Properties"
Public Property NavigateURL() As String
Get
Return If(ViewState("NavigateURL") Is Nothing, "", ViewState("NavigateURL").ToString())
End Get
Set(ByVal value As String)
ViewState("NavigateURL") = value
End Set
End Property
#End Region
Protected Overrides Sub AddAttributesToRender(ByVal writer As System.Web.UI.HtmlTextWriter)
If (Me.Page IsNot Nothing) Then
Me.Page.VerifyRenderingInServerForm(Me)
End If
Me.EnsureID()
writer.AddAttribute(HtmlTextWriterAttribute.Id, Me.ClientID)
If (Not String.IsNullOrEmpty(Me.CssClass)) Then
writer.AddAttribute(HtmlTextWriterAttribute.Class, Me.CssClass)
End If
If (Not Me.Enabled) Then
writer.AddAttribute(HtmlTextWriterAttribute.Disabled, "disabled")
End If
If (Not String.IsNullOrEmpty(Me.NavigateURL) AndAlso Me.Enabled) Then
' Set the href to be our navigateUrl.
writer.AddAttribute(HtmlTextWriterAttribute.Href, Me.ResolveUrl(Me.NavigateURL))
End If
If (Me.Enabled) Then
Dim customScript As String = Me.OnClientClick
If (customScript.Length > 0 AndAlso Not customScript.EndsWith(";")) Then
customScript = customScript + ";"
End If
Dim opts As PostBackOptions = Me.GetPostBackOptions()
Dim evt As String = Nothing
If (opts IsNot Nothing) Then
evt = Me.Page.ClientScript.GetPostBackEventReference(opts)
End If
' The onclick now becomes our postback, and the appended custom script.
writer.AddAttribute(HtmlTextWriterAttribute.Onclick, String.Format("{0}; {1} return false;", evt, customScript))
End If
End Sub
End Class -
Different SQL between C# and vb.net using LINQ to SQL causes performance issues
Hi All,
I am currently working on a project and we are using VB.NET, I am using LINQ to SQL for my data access. I have just implemented my search query and thought I would check the generated SQL's execution plan and found that the subtree cost was about 7.3. I know that I get different SQL between C# and VB.NET when using LINQ to SQL, as VB.NET seems to add a WHERE COALESCE instead of the straight WHERE that C# will do. In the past I did a quick check on a small query to see if it would make a difference and found that there was not a noticable one.
Now having a larger more complex query I thought I would check the execution plan for the same query but written in C#, I now get a much smaller SQL query and the subtree cost drops from 7.3 to 0.1. A big difference IMO. Has anyone come across this before and what are your throughts on this. It baffles me that you would get such a difference in queries between the two languages. -
Issues using HyperLink control with an image in a URL Rewriting scenario
Hey All,
I was using the HyperLink control in my page and added URL Rewriting to my page so that for example:
http://site/test/test/default.aspx would be rewritten to http://site/default.aspx. I had a HyperLink control on the default page like so:
<asp:HyperLink ID="hl1" runat="server" NavigateUrl="~/test.aspx" ImageUrl="~/test.jpg" Text="A"></asp:HyperLink>
And I was getting the dreaded error: Cannot use a leading .. to exit above the top directory...
Looking into this a little more if you remove the ImageURL property or even set it to be /test.jpg it will work fine, so conluded it must be something to be with the ImageUrl property in the control. Digging into reflector it looks like that when the HyperLink control renders it creates a new Image object and sets the ImageUrl of that to be ResolveClientUrl(url), internally the Image control also does a ResolveClientUrl again on that URL and I think this is where the issue is.
My solution was to create a FixUrl method in my utility class which would convert replace ~/ in a url with the current application base path hence giving me an absolute URL. This is also handy to use in your pages to set the urls of your CSS, JS etc.
Public Shared Function FixUrl(ByVal inURL As String) As String
Return If(inURL.StartsWith("~"), _
HttpContext.Current.Request.ApplicationPath & inURL.Substring(1), _
inURL).Replace("//", "/")
End Function
I would now assign my ImageUrl property in code i.e. img1.ImageUrl = FixURL("~/test.jpg") and this now works well.
If anyone has come past this before suggestions or ideas they would be appreciated.
Thanks
Stefan