SPDataSource – every developer’s friend (part 2)

SPDataSource – a refresher

So last time in part 1 of this 2-part series, we saw how SPDataSource is a great option for fetching data from lists since not only does it do the actual work of fetching the items for you, it also does this without any C#/VB.Net code. We can retrieve all the items from the list, or optionally supply a CAML query along with the list details if we wish to filter/sort the items. So as I showed in part 1, we can easily display a dropdown containing the items from a list with the following markup:


<SPWebControls:SPDataSource runat="server" ID="dsPersonTitles" DataSourceMode="List" 
SelectCommand="<Query><OrderBy><FieldRef Name='SortOrder' Ascending='true' /></OrderBy></Query>"
<SelectParameters>
<asp:Parameter Name="WebUrl" DefaultValue="/configuration/" />
<asp:Parameter Name="ListName" DefaultValue="PersonTitles" />
</SelectParameters>
</SPWebControls:SPDataSource>

<asp:DropDownList runat="server" ID="ddlPersonTitles" CssClass="title" DataSourceID="dsPersonTitles" DataTextField="Title" DataValueField="ID">
</asp:DropDownList>




We also saw how SPDataSource offers more than just retrieving items from a list, with the following other ‘modes’ (see part 1 for more details on these):

  • CrossList – similar to doing a query with SPSiteDataQuery across all lists in a site collection
  • ListItem – show field values from a single list item

  • Webs – lists all webs in a site collection

  • ListOfLists – lists all lists in a web

What I want to focus on this time is how to use parameters with SPDataSource, since when using the control for real you’ll often want to do this.

Parameters with SPDataSource

SPDataSource works like other .Net data source controls, so the key to passing parameters is using one of the .Net 2.0 parameter classes, either declaratively (in markup) or in code. The example above shows using the basic Parameter class by setting the DefaultValue property to a known string, but the following parameter types can also be used (though note I haven’t tried them all and the SPD Team Blog article I mentioned says somewhat vaguely that "most" of them can be used!):

Effectively using one of these saves you writing code to read the value from the respective location and passing it to SPDataSource yourself. I think that ControlParameter and QueryStringParameter are possibly of the most value, though all could be interesting depending on your requirements. As an example, to get the value a user selected earlier from a dropdown containing a list of lists and pass it to a SPDataSource control I would need:


<SelectParameters>
<asp:Parameter Name="WebUrl" DefaultValue="/configuration/" />
    <asp:ControlParameter Name="ListName" ControlID="ddlLists"
PropertyName="SelectedValue"/>
</SelectParameters>

I seemed to have some control execution lifecycle fun with ControlParameter but it did work in the end. To pull the value from a ‘userID’ querystring parameter I would need:


<SelectParameters>
<asp:QueryStringParameter Name="userId" QueryStringField="userId" />
</SelectParameters>

And that’s not all – I can also drop a parameter value into a string such as a CAML query used in the earlier example of ‘List’ mode:


<SPWebControls:SPDataSource runat="server" ID="dsPersonTitles" DataSourceMode="List"
SelectCommand="<Query><OrderBy><FieldRef Name='{SortField}' Ascending='{SortAsc}' /></OrderBy></Query>">
<SelectParameters>
<asp:Parameter Name="WebUrl" DefaultValue="/configuration/" />
<asp:Parameter Name="ListName" DefaultValue="PersonTitles" />
<asp:QueryStringParameter Name="SortField" QueryStringField="SortField" DefaultValue="SortOrder" />
<asp:QueryStringParameter Name="SortAsc" QueryStringField="SortAsc" DefaultValue="true" />
</SelectParameters>
</SPWebControls:SPDataSource>

Notice here I’m dynamically specifying the sort field and direction from querystring parameters. Cool stuff.

Even cooler is the idea of building your own parameter control – one that strikes me is one for retrieving values from a user’s SharePoint profile (since the ProfileParameter listed above refers to ASP.Net profiles). Scott Mitchell has a great guide to this at Accessing and Updating Data in ASP.NET 2.0: Creating Custom Parameter Controls.

Summary

So we’ve covered a lot of ground there, so here’s a recap of why the SPDataSource is your friend:

  • Can bind to any control which can do data-binding – DropdownList, ListBox, CheckBoxList are some obvious candidates, but consider also Repeater, DataGrid and SharePoint DataView/SPGridView controls

  • Can easily get parameters from other controls, querystring, session, form values etc. (or write some code to fetch from another location)

  • Can use a variety of modes to make different queries e.g. items in a list, properties of a list item, webs in a site etc.

If you want to see more I recommend reading SPDataSource and Rollups with the Data View – this emphasises using SPDataSource with SharePoint DataViews but also has some good examples I haven’t covered, such as using the ‘CrossList’ mode.

SPDataSource – every SharePoint developer’s friend (part 1)

Sooner or later, nearly every SharePoint developer needs to write code to retrieve all the items from a list and display them – either on the page, or often in a control like a dropdown list control. An example could be retrieving a list of countries, or perhaps person titles for a form:

DropdownFromList

Clearly there are benefits from storing such values in a list, since we (or the client) can then add/edit/delete items easily. To implement this, the developer’s first thought might be to write code like this:

private void bindPersonTitles()
{
// the name of the DropDownList control we are populating is ddlPersonTitles..
using (SPWeb configWeb = SPContext.Current.Site.AllWebs["configuration"])
{
SPList titlesList = configWeb.Lists["PersonTitles"];

foreach (SPListItem titleItem in titlesList.Items)
{
ddlPersonTitles.Items.Add(new ListItem(titleItem.Title, titleItem.ID.ToString()));
}
}
}


Which is fine. Except if we want to filter or sort the list items, we really should use a CAML query instead of iterating through all the items – the code below shows this (sorting on a column called ‘SortOrder’), and also has a slight twist on the previous example in that I’m using data-binding rather than looping through the items ‘manually':


private void bindPersonTitlesByCamlQuery()
{
using (SPWeb configWeb = SPContext.Current.Site.AllWebs["configuration"])
{
SPList titlesList = configWeb.Lists["PersonTitles"];
SPQuery query = new SPQuery();
query.Query = "<OrderBy><FieldRef Name=\"SortOrder\" /></OrderBy>";
SPListItemCollection titlesItems = titlesList.GetItems(query);

// showing alternative of using data-binding rather iterating through items..
ddlPersonTitles.DataSource = titlesItems;
ddlPersonTitles.DataTextField = "Title";
ddlPersonTitles.DataValueField = "ID";
ddlPersonTitles.DataBind();
}
}

Fine again. Except I can’t help thinking "all this just to take the items from a list and put them in a dropdown??" Surely there must be a better way. And what did Microsoft do every time they needed to do this, surely they didn’t repeat the above code in every place in SharePoint? The answer is no, they used this:

SPDataSource

In short, SPDataSource is a web control which implements IDataSource and saves you writing code like the above. The great thing is that it is extremely flexible, and as we’ll see, can be used for more than you might think. The best thing though, is that being a control it can be used declaratively, so I can bind my dropdown to the list without writing a single line of C# or VB.Net code – all I have to do is set properties correctly. We’ll go through the detail in a second, but the markup to replace the last code sample would look like:


<SPWebControls:SPDataSource runat="server" ID="dsPersonTitles" DataSourceMode="List" 
SelectCommand="<Query><OrderBy><FieldRef Name='SortOrder' Ascending='true' /></OrderBy></Query>"
<SelectParameters>
<asp:Parameter Name="WebUrl" DefaultValue="/configuration/" />
<asp:Parameter Name="ListName" DefaultValue="PersonTitles" />
</SelectParameters>
</SPWebControls:SPDataSource>

<asp:DropDownList runat="server" ID="ddlPersonTitles" CssClass="title" DataSourceID="dsPersonTitles" DataTextField="Title" DataValueField="ID">
</asp:DropDownList>

So we’re doing the following:
  • setting the ‘DataSourceMode’ for the SPDataSource is set to ‘List’ – we’ll examine other possible values shortly

  • setting the ‘SelectCommand’ to the CAML query we want to use – here we’re just sorting on the ‘SortOrder’ field once more

  • telling the SPDataSource which list we want to use by supplying ASP.Net 2.0 parameter objects named ‘WebUrl’ and ‘ListName’ – we’ll dive more into this later

  • finally we bind the dropdown to the data by specifying the DataSourceID to the ID we gave our SPDataSource, and also say which fields in the resultset we want to use for the ‘Text’ and ‘Value’ of the dropdown. Incidentally I recommend using the ID for the value and the Title for the text (as shown above) so that it’s easy to create an SPLookupValue to update a list item – more on this in part 2

We’re only just starting to see the power of SPDataSource, but I love this approach for a couple of reasons:
  • Details of my query aren’t specified in compiled code, so if anything about the list changes (e.g. we restructure our site) I don’t have to recompile and redeploy assemblies

  • Less custom code, less bugs!

  • Setting properties is arguably simpler than writing code

So let’s dive deeper into what we can do – we’ll cover ‘modes’ of SPDataSource in this article and how to dynamically pass parameters to control the query in part 2.

The different ‘modes’ of SPDataSource

SPDataSource isn’t just limited to fetching the items from a list (DataSourceMode = ‘List’). Other possibilities are:

  • CrossList – similar to doing a query with SPSiteDataQuery across all lists in a site collection (for a sample of this see the SharePoint Designer Team blog post linked at the end of this article)

  • ListItem – show field values from a single list item

  • Webs – lists all webs in a site collection

  • ListOfLists – lists all lists in a web

For the last 2 modes I was able to bind but had some difficulty working out values to use for the ‘DataTextField’/’DataValueField’ of my control. I was trying to simply get the web or list name, but none of the obvious values such as ‘Title’, ‘ListName’ etc. were in the resultset. I was unable to find any other information on this but I’m sure some more trial and error would solve it. The ‘ListItem’ mode can be interesting – in the following sample I’m binding a single list item to a DataGrid to show selected fields from the item, which itself is selected by using the ‘ListItemID’ property:



<SPWebControls:SPDataSource runat="server" ID="dsPeople" DataSourceMode="ListItem" UseInternalName="true"> 
<SelectParameters>
<asp:Parameter Name="WebUrl" DefaultValue="/configuration/" />
<asp:Parameter Name="ListID" DefaultValue="34F91B0C-FCF2-455A-ABBA-67724FB4024A" />
<asp:Parameter Name="ListItemID" DefaultValue="1" />
</SelectParameters>
</SPWebControls:SPDataSource>

<asp:GridView ID="grdPeople" runat="server" DataSourceID="dsPeople"
AutoGenerateColumns="False">
<Columns>
<asp:BoundField DataField="FullName" HeaderText="Blogger name" />
<asp:BoundField DataField="WorkCity" HeaderText="City" />
<asp:BoundField DataField="Blog_x0020_URL" HeaderText="Blog URL" />
</Columns>
</asp:GridView>

This would give something like this, based on an underlying list item which has these fields (no formatting yet applied):

SPDataSource_ListItem_DataGrid

I found I had to specify UseInternalName = "true" and use the ListID rather than ListName parameter in this mode.

Next time – passing parameters to SPDataSource

So far we’ve looked at supplying parameters by using a standard ASP.Net parameter control and specifying the value in the DefaultValue’ property. In fact, ASP.Net has a whole range of parameter controls which can do the work of retrieving a parameter from somewhere and passing it to the SPDataSource, so that’s what we’ll look at next time. Additionally, since we’re often using SPDataSource to bind data to form controls, we’ll look at the common scenario of getting the selected item out of the form control to save back to a lookup field in SharePoint.

<updated>That link to the SPD blog article I mentioned but forgot to link to is http://blogs.msdn.com/sharepointdesigner/archive/2007/04/24/spdatasource-and-rollups-with-the-data-view.aspx – the focus here is mainly on using SPDataSource with a DataView, but there’s some great info and samples.</updated>

Received MVP award for SharePoint!

Had notification from Microsoft today that I’m now a SharePoint MVP :-)

This is great news, I’m really thrilled to be recognized for the community stuff I’ve done over the past year, and personally I know I’ve been impressed by the work of so many existing SharePoint MVPs, so it’s a big honor to be part of that group. I’m particularly grateful to the people who nominated me, thanks guys. It was weird having to look back to fill in the spreadsheet MS ask you to complete to be considered for MVP – I guess some of the key highlights for me were:

I guess I’ll enjoy putting the MVP image on my blog etc., but the biggest reward is without doubt when someone leaves a positive comment or mentions in person that they’ve found the articles or tools useful – I’m never sure if people realize how much this is listened to. Anyway, I’m busy on the next version of the Wizard and some other articles, so you’ll hear a lot more from me in the future.

Still a long way to go until I’m Andrew Connell or any number of the others though ;-)

P.S. Great to hear my mate Vince received it as well, definitely well deserved..