This one’s going to be long, but for those of you who’ve felt the first 3 in this series were too easy I promise this one’s tougher J. Let’s say you want to list all the customers from a table in a ComboBox, and update the UI based on which one is selected. To do this we’ll need to bring back two fields from...
About two years ago I posted some code that shows how to dynamically construct LINQ queries at runtime. On average there's a couple questions per month about trying it in some edge case, and usually the support already exists within the API. Recently though someone posted a question that has to do with Datasets and Joins that raised som...
Most XSLT programmers are familiar with this XSLT transform to copy an XML file. <?xml version="1.0" encoding="utf-8"?><xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"> <xsl:output method="xml" indent="yes"/> <xsl:template match="@* | node()"> ...
Last week I got the chance to visit the Toronto .NET User Group and give a talk on all the great new language features in VB2008. It was great to see so much excitement around LINQ and especially XML Literals! The slides and demo code are posted at the link below; here’s the session abstract (with links inserted so you can find more in...
Last week I went on a user group tour around Southern California. I've uploaded the materials from my talk: You can find these all posted together on the following Code Gallery page.The demo requires installation of Refactor!, which is a 3rd party tool available for free on MSDN. I also pointed out a number of resources at the end of the tal...
LINQ at its core requires any data source to be queryable, which basically means it must implement IEnumerable. (It’s actually a bit more complicated than that, for a full explanation see section 11.21.2 of the Visual Basic 9.0 Language Specification). Now when working with LINQ to Dataset we have a problem: DataTable does not imp...
Recently I got a customer question about how to use LINQ to Dataset in an .aspx file. The compiler was complaining that it couldn't find the AsEnumerable method that allows LINQ to work over a DataTable ("AsEnumerable is not a member of 'DataTable'"). The code he sent looks correct, so why is the compiler not picking up the extension me...
In the last two XML cookbook entries, we talked about the technique of using the ReplaceWith method to perform an identity transform. While this technique may meet your needs, it can introduce a problem in your code commonly referred to as the “Halloween” problem. Let’s take a look at what the problem is, and how to solve it. (For details on the “...
Recipe 3 showed one way to work with mixed XML content using the XML Descendant axis property and the ReplaceWith method. This is one way to do an identity transform and we’ll look at another method in a later post. There is a key capability not mentioned in Recipe 3 that you will need for fully-functioning identity transforms. That is the co...
An identity transform in XSLT does just what the name implies: replace the identity of an element or attribute with a new identity. Identity transforms are especially critical when dealing with XML markup that is less rigid in its structure. Consider a documentation structure for news articles. Whenever a title is referred to within an article, it ...
