How can I retrieve a list of workitems from TFS in C#?

Question

I'm trying to write a project reporting tool in WPF / C#. I want to access all the project names on our TFS (Team Foundation Server), and then display statistics for each work item in a given project.

I've got the project names, but getting the actual work items is what's giving me a hard time. Here's what I've got so far:

public const string tfsLocation = "http://whatever";

// get the top list of project names from the team foundation server
public List<string> LoadProjectList()
{
    var tpc = TfsTeamProjectCollectionFactory.GetTeamProjectCollection(new Uri(tfsLocation));
    var workItemStore = new WorkItemStore(tpc);
    var projects = (from Project project in workItemStore.Projects select project.Name).ToList();

    return projects;
}

public string GetProjectInfo(string targetProject)
{
    string info = String.Empty;

    var tpc = TfsTeamProjectCollectionFactory.GetTeamProjectCollection(new Uri(tfsLocation));
    var workItemStore = new WorkItemStore(tpc);

    foreach (Project project in workItemStore.Projects)
    {
        if (project.Name == targetProject)
        {
            info += String.Format("Project: {0}\n\n", project.Name);

            info += "Work Item Types:\n";
            foreach (WorkItemType item in project.WorkItemTypes)
            {
                info += String.Format("-   {0}\n", item.Name);
                info += String.Format("    -   Description: {0}\n", item.Description);
                info +=               "    -   Field Definitions:\n";

                foreach (FieldDefinition field in item.FieldDefinitions)
                {
                    info += String.Format("        -   {0}\n", field.Name);
                }
                info += "\n";
            }
        }
    }

    return info;
}

GetProjectInfo sends back some helpful info about what's in each project, but so far it looks like I'm only seeing the definitions of what the WorkItems consist of, and not the actual WorkItems themselves. I think the programming I've written is looking in the wrong place.

From Microsoft's definition of WorkItem, (http://msdn.microsoft.com/en-us/library/microsoft.teamfoundation.workitemtracking.client.workitem.aspx) it looks like it's inside WorkItemTracking.Client, but not inside the WorkItemStore, and I'm not sure where to go to access it.

FINAL VERSION:

Here's the updated version of my function, after referencing the below answer. This just returns a long string of the work item names with new lines between, for printing out, which is all I'm trying to get working (for now).

public string GetProjectInfo(string targetProject)
{
    string info = String.Empty;

    var tpc = TfsTeamProjectCollectionFactory.GetTeamProjectCollection(new Uri(tfsLocation));
    WorkItemStore workItemStore = new WorkItemStore(tpc);

    Query query = new Query(workItemStore, "SELECT * FROM WorkItems WHERE [System.TeamProject] = @project", new Dictionary<string, string>() { { "project", targetProject } });

    WorkItemCollection wic = query.RunQuery();

    foreach (WorkItem item in wic)
    {
        info += String.Format("{0}\n", item.Title);
    }

    return info;
}

Solution

You need to use WIQL queries to get actual work items you are interested in, e.g. to get all work items for a particular project:

using Microsoft.TeamFoundation.WorkItemTracking.Client;

Query query = new Query(
     workItemStore, 
     "select * from issue where System.TeamProject = @project",
     new Dictionary<string, string>() { { "project", project.Name } }
);

var workItemCollection = query.RunQuery();
foreach(Microsoft.TeamFoundation.WorkItemTracking.Client.WorkItem workItem in workItemCollection) 
{
   /*Get work item properties you are interested in*/
   foreach(Microsoft.TeamFoundation.WorkItemTracking.Client.Field field in workItem.Fields)
   {
      /*Get field value*/
      info += String.Format("Field name: {0} Value: {1}\n", field.Name, field.Value);
   }
}