Open the SharePoint 2010 Web site that you want to add the Web Parts to (such as http://localhost/sites/SampleWebPartSite) in Internet Explorer.

Click Site Actions, click More Options, and then click Custom List.

In the Name box, type Projects and then click Create.

On the List Tools tab, click List, and on the Manage Views group, click Modify Views.

Clear all Column Name options and then select the ID and Title options. Click OK.

Click Add new item and add the information in the first row (ignore the header row) of Table 1. The ID fields updates automatically.

Repeat step 6 for the remaining rows of Table 1.

Start Visual Studio 2010, click File, point to New, and then click Project.

Click the Visual C# node in the Installed Templates section, click SharePoint, and then click 2010.

Click the SharePoint Empty Project project template (see Figure 1), provide a name (such as, ConnectTwoWebParts), a location for your project, and then click OK.

In the What local site do you want to use for debugging list, select the site to use (such as http://localhost/SampleWebPage). Also select the Deploy as a farm solution option and then click Finish.

The ConnectTwoWebParts project is created and Solution Explorer is displayed.

In Solution Explorer, right-click ConnectTwoWebParts, point to Add, and then click New Item.

In the Add New Item dialog window, click Visual C#, click Code, and then select Interface from the available templates.

Type IProject in the Name box and then click Add.

In Solution Explorer, double-click the IProject.cs file.

Change the visibility of the interface to public by prefixing the keyword public to the interface declaration (see Figure 2).

Insert the following code inside the IProject interface.

int Id { get; } 
string Name { get; }

In Solution Explorer, right-click ConnectTwoWebParts, point to Add, and then click New Item.

Click the Visual C# node in the Installed Templates section, click SharePoint, and then click 2010. Select Web Part from the available templates.

Type ProviderWebPart in the Name box and then click Add.

The provider Web Part is added to the project.

In Solution Explorer, double-click ProviderWebPart.cs to open the code file.

In the ProviderWebPart class declaration, replace the class from which the ProviderWebPart class is inheriting by changing WebPart to the following:

Microsoft.SharePoint.WebPartPages.WebPart, IProject

Insert the following code immediately after the opening bracket ({) in the ProviderWebPart class declaration. This code block implements the IProject Web Part connection interface and adds a local variable to the Web Part.

DropDownList _projectPicker = null;  
int IProject.Id 
{ 
    get { return int.Parse(_projectPicker.SelectedValue); } 
} 
 
string IProject.Name 
{ 
    get { return _projectPicker.SelectedItem.ToString(); } 
}

Insert the following code in the CreateChildControls subroutine.

base.CreateChildControls;
try 
{ 
    _projectPicker = new DropDownList(); 
 
    using (SPSite spSite = new SPSite(SPContext.Current.Web.Url)) 
    using (SPWeb spWeb = spSite.OpenWeb()) 
    { 
        SPList projectsList = spWeb.Lists["Projects"]; 
 
        foreach (SPListItem project in projectsList.Items) 
        { 
            _projectPicker.Items.Add(new ListItem(project.Name, project.ID.ToString())); 
        } 
    } 
    _projectPicker.AutoPostBack = true; 
 
    this.Controls.Add(_projectPicker); 
} 
catch (Exception ex) 
{ 
    this.Controls.Clear(); 
    this.Controls.Add(new LiteralControl(ex.Message)); 
}

Insert the following ConnectionProvider property after the CreateChildControls subroutine. This provides the connection provider interface point for the ProviderWebPart.

[ConnectionProvider("Project Name and ID")] 
public IProject NameDoesNotMatter() 
{ 
    return this; 
}

Delete the RenderContents subroutine, if it exists.

In Solution Explorer, right-click ConnectTwoWebParts, point to Add, and then click New Item.

Click the Visual C# node in the Installed Templates section, click SharePoint, and then click 2010. Select Web Part from the available templates.

Type ConsumerWebPart in the Name box and then click Add.

The consumer Web Part is added to the project.

In Solution Explorer, double-click ConsumerWebPart.cs to open the code file.

Insert the following code after the opening bracket ({) of the ConsumerWebPart class declaration.

IProject _provider = null; 
Label _lbl = null;

Insert the following code in the CreateChildControls subroutine.

base.CreateChildControls;
try 
{ 
    _lbl = new Label(); 
 
    if (_provider != null) 
    { 
        if (_provider.Id > 0) 
        { 
            _lbl.Text = _provider.Name + " was selected."; 
        } 
        else 
        { 
            _lbl.Text = "Nothing was selected."; 
        } 
    } 
    else 
    { 
        _lbl.Text = "No Provider Web Part Connected."; 
    } 
 
    this.Controls.Add(_lbl); 
} 
catch (Exception ex) 
{ 
    this.Controls.Clear(); 
    this.Controls.Add(new LiteralControl(ex.Message)); 
}

Insert the following ConnectionConsumer property after the CreateChildControls subroutine. This provides the connection consumer interface point for the ConsumerWebPart Web Part.

[ConnectionConsumer("Project Name and ID")] 
public void ThisNameDoesNotMatter(IProject providerInterface) 
{ 
    _provider = providerInterface; 
}

Delete the RenderContents subroutine, if it exists.

In Solution Explorer, right-click ConnectTwoWebParts and then click Deploy.

Open Internet Explorer and browse to the Web site that you specified for the project.

Click the Site Actions menu and then click More Options.

Scroll and then click Web Part Page. Type SampleWebPartPage in the Name box and then click Create.

SharePoint Foundation creates the Web Parts page and opens it in Edit mode.

Click one of the Web Part zones in the blue box.

Select Custom in the Categories box (see Figure 3), select the ConsumerWebPart, and then click Add.

This adds the ConsumerWebPart to the page as shown in Figure 4.

Repeat these steps to add the ProviderWebPart to a different Web Part zone. Both Web Parts are now displayed on the page as shown in Figure 5.

In this task, you connect the Provider Web Part to the Consumer Web Part.

Point to Connections, point to Send Project Name and ID To, and then click ConsumerWebPart.

You should see the project title displayed in the ConsumerWebPart Web Part.

Make a different selection in the Provider Web Part list. The change in title is then reflected in the Consumer Web Part zone as shown in Figure 6.