Unlocking the Mysteries of Data View Web Part XSL Tags – Part 13 – Miscellaneous: String Functions

Cross-posted from EndUserSharePoint.com…

In the last article, I talked about teasing out the various parts of the values in Person or Group column values. To do this, I relied on the substring functions which are available to us in XSL. In this article, I’ll go over a few of those string functions and show you how useful they can be.

What you create a new variable with <xsl:variable> or use <xsl:value-of> to display the contents of a variable or column (among other things), you have many different options available to you in the select attribute. When you first type the equal sign after the select, you’ll see a dropdown menu in SharePoint Designer. The first option in that dropdown is XPath Expression Builder:

When you click on the XPath Expression Builder, you can build up more complex XPath expressions with the Builder to help you through the process. In this article, we’re going to focus on a few of the Text / String functions:

As you click on each of these functions, you’ll see how to use them on the right side, as in the screenshot above showing the concat definition. I won’t repeat those definitions here as there are many other great posts out there that cover them. Instead, I’ll go over a few tricks you’ll need to know to use these functions to do cool stuff. If you’re used to using string functions in other languages, you might get frustrated with this set of functions. I know I was early on, and it took some getting used to them before I was able to crank out useful XPath expressions easily.

substring-before and substring-after

These twins work great together. Let me repeat an example from the previous article on Person or Group columns. Here’s what a typical Person or Group column value might look like:

If you don’t want to display the user’s name as a hyperlink, you can substring out the actual name:

<xsl:variable name="UserName" select="substring-after(substring-before(substring-after(@Author, ‘ID=’), ‘&lt;’), ‘&gt;’)"/>

This was probably clear as mud when I showed it before, but let’s break it apart a little.

First, we grab the text after the ‘ID=’ string:

substring-after(@Author, ‘ID=’)

Then the text before the ‘<’ in the remaining text:

substring-before(substring-after(@Author, ‘ID=’), ‘<’)

And finally then the text after the ‘>’ in the remaining text:

substring-after(substring-before(substring-after(@Author, ‘ID=’), ‘<’), ‘>’)

Hopefully the pictures make it a little more obvious how we’re whittling down the big long string into what we want.

string-length

string-length is especially useful when we want to test for the existence of a value. Keep in mind that all values coming back to us in the DataSource are always coming stored as text in XML. SharePoint Designer parses apart the XML for us so that we don’t have to think about the actual representation. When a value is “empty” (in other languages you might test for a null value or an undefined value, etc.), then it has no value. We can test for the existence of the value by checking the string-length:

<xsl:choose>
  <xsl:when test="string-length(@Title &gt; 0)">
    <xsl:value-of select="@Title"/>
  </xsl:when>
  <xsl:otherwise>
    The Title is empty.
  </xsl:otherwise>
</xsl:choose>

translate

translate lets you replace one character with another in a text value. Here’s one spiffy trick you can use it for: converting a string to all upper case for reliable comparisons between strings.

<xsl:variable name="UTitle" select="translate(@Title, 'abcdefghijklmnopqrstuvwxyz', 'ABCDEFGHIJKLMNOPQRSTUVWXYZ')"/>

What this does is replace the instances of each lowercase letter with their uppercase equivalent. If you are doing this just for display, then I would encourage you to use a CSS class with text-transform:uppercase, but this trick is great when you need to work with the strings in your XSL logic.

This is an example of nice little template to keep around in case you need it. In larger projects, I’ll usually build up a utilities.xsl file and store it in /Style Library/XSL Style Sheets. In that file, I’ll store reusable utility templates to do things like this uppercase conversion. Then I include the utility.xsl file in DVWPs wherever I need it using the <xsl:import> tag. (No, I haven’t covered that one in this series. Yet.)

Obviously, there are a few more of these string functions available to use in your XPath expressions. I just wanted to show you a few of the little tricks that you can do with them that turn out to be useful over and over again.

In the next article, I’ll go into some more depth on the ddwrt namespace.