Bilbro Bloggins

This is the first part of a multipart blog series.

1. In part one, we created a simple SharePoint Web Part which displayed a text label that could be set via the Web Part Properties Editor.
2. In part two of this blog series, we extended the simple SharePoint Web Part by adding a dropdown list box and populating it with values from a SharePoint list.
3. In part three, we add the capabilities to use the selected value in the dropdown list box to filter various SharePoint lists on the page.
4. In part four, you can download the Visual Studio 2008 project solution.

Blog Series Summary:

As a part of a proof of concept site I was creating in SharePoint, I wanted to learn how to create a web part in SharePoint that can communicate to other web parts on the page.  The web part that I wanted to create was a drop-down list box that would display a list of projects.   Selecting a project on the drop-down list would then drive the contents of the various SharePoint project lists (issues, notes, risks, etc…) on the SharePoint page.

Part Three:

In part three of this blog, we’ll add the capabilities to use the selected value in the dropdown list box to filter various SharePoint lists on the page.

Step 1 – To make a filter provider, we are going to implement the interface ITransformableFilterValues.  Update your class definition to include the ITransformableFilterValues interface.

public class DropDownFilterBlog : System.Web.UI.WebControls.WebParts.WebPart, ITransformableFilterValues

Step 2 – Now we’ll need to implement the various properties of the ITransformableFilterValues interface.

public bool AllowAllValue
{
    get { return false; }
}
public bool AllowEmptyValue
{
    get { return true; }
}
public bool AllowMultipleValues
{
    get { return false; }
}
public string ParameterName
{
    get
    {
        if ((this.ValueField != null) && (this.ValueField.Length > 0))
        {
            return this.ValueField;
        }
        else
        {
            return "Unknown";
        }
    }
}
public System.Collections.ObjectModel.ReadOnlyCollection<string> ParameterValues
{
    get
    {
        string selectedValue = String.Empty;
        if ((_sourceDropDownList!=null) && (_sourceDropDownList.SelectedItem != null))
        {
            selectedValue = _sourceDropDownList.SelectedItem.Value;
        }
        string[] values = new string[] { selectedValue };
        return new ReadOnlyCollection<string>(values);
    }
}

AllowAllValue, AllowEmptyValue and AllowMultipleValues are pretty straightforward.  Since we are dealing with a dropdown list box we can only have one value selected.  ParameterName is set to return a dynamic value based upon what you have set as the dropdown list box value property.  The value of ParameterName is displayed in the Web Part Connection property editor.   ParameterValues is the value sent to any consumer web parts (i.e. this is the value selected in the dropdown list box that we will pass to other web parts on the page).

using statements needs – The ReadOnlyCollection reference will require the following to be added to your list of using statements at the top of the class.

using System.Collections.ObjectModel;

Step 3 – And finally, we just need to a method that creates an instance of our filter provider.

[ConnectionProvider("DropDown Filter", "ITransformableFilterValues", AllowsMultipleConnections = true)]
public ITransformableFilterValues SetConnectionInterface()
{
    return this;
}

The ConnectionProvider has multiple overloads.   The first parameter shows up in the edit web part Connection menu option.  The second parameter is the name that shows ups in the web part connections editor.  The third parameters allows this web part to send it’s filter information to multiple consumers.

Step 4 – If you have not done so, set the URL to your SharePoint server:  Right click project -> Properties -> Debug -> Start browser with URL.

Step 5 – Build and Deploy the web part to your SharePoint server. Right click project –> Deploy

Step 6 – If you have not down so, add the web part to a page and set the Dropdown filter properties to a SharePoint list.

Step 7 – Create a couple of SharePoint lists that have lookup values to the SharePoint lists you specified in Step 6.

Step 8 – Add some data to those lists.

Step 9 – Add those lists to your web page.

Step 10 – Set connections to your two lists from the DropDown Filter Web Part.  From your Dropdown Filter Web Part edit menu: edit->Connections->Send DropDown Filter To –>YourList

And then Connection Editor appears.  Match the field from your dropdown (in bold) to the appropriate field to filter on in the list.  Note if then field you want to field on is not available, you might need to edit the view of your list to add the field.   Special note, if you list is from a BDC Web Part list then you can filter any field from the BDC and not just those that are showing.

Do this for both lists on your SharePoint Web Part page.

Step 11 – Now as you change values in the dropdown list you should see the other lists filtering down to the selected item.

And that concludes part three.  In part four, you can download the entire Visual Studio project.