Skip to main content

Custom Classes and LINQ To SQL Group By

I spent a good part of my morning trying to get LTS to return my custom class as a result of a group by instead of an anonymous type. Most of the samples I found on the web for Group By returned anonymous types and the ones that didn't were from early versions and I couldn't get them to work.

The problem I was having was getting the column I was grouping on mapped. I created a class called DescriptionCounts that had two properties Description (string) and Count (integer). The following code will correctly map a group by query to this class.

Dim i = From b In dc.Barriers _  
  Group By b.BarrierType.Description Into g = Group _ 
  Select New DescriptionCounts _ 
  With {.Description = Description, .Count = g.Count}

The main thing to notice is that when the Description property gets mapped, it is mapped to a variable named Description (.Description = Description -- notice that there is no prefix) and not to a property of b.

All of the aggregate functions require that you use the Group command (g = Group).

Technorati Tags: ,


Popular posts from this blog

JavaScript function to automatically add slashes to date

In converting an old Windows app to a browser app, the user wanted to be able to enter dates without the slashes. Here's a simple jscript: 1:// Function to convert short date string (MMddyy) 2:// or (MMddyyyy) to a date string (mm/dd/yyyy). 3:// txtBox is the actual textbox control 4:// with the value to be processed. 5:function FixShortDate(txtBox) { 6:if (txtBox == null) { 7:return'' } 8: 9:var re = new RegExp(/(\d{6})(\d{2})?/); 10: 11:if (re.test(txtBox.value)) 12: { 13:if (txtBox.value.length == 8) { 14: txtBox.value = txtBox.value.substring(0, 2) + '/' + txtBox.value.substring(2, 4) + '/' + txtBox.value.substring(4, 8) 15: } 16: 17:if (txtBox.value.length == 6) { 18:if (txtBox.value.substring(4, 6) < 20)

Migrating Legacy Apps to the New SimpleMembership Provider

Asp.Net MVC4 uses the new SimpleMembership provider, changes the table structure and adds a new hashing algorithm. The reasons for the changes can be found in this article by Jon Galloway. This article shows how to migrate your existing apps to the new provider.I’m assuming that you stored your passwords in the unrecoverable SHA-1 format. If you didn’t, then you’ll have to change a couple of things. All of my apps are done this way so… I’m also assuming that you have created the basic skeleton of the new app and ran it once so the correct tables will be created.First, we’ll look at the new tables. Previously, we had all of those aspnet_xxxxxx tables. Here’s the new ones.UserProfileContains all of the elements relevant to the user. This is a combination of the aspnet_Users table and the aspnet_Profiles table.webpages_MembershipStores the password info when not using OAuth, Live, Facebook, etc. This table is somewhat of a match to the aspnet_Membership table.webpages_OAuthMembershipStor…