TFS | Get Linked User Story to workitem using c#

I want to fetch user story which is linked to a test case. I have test case details but want to fetch the linked user story through it in c#.

Not able to find any helpful reference online.

You could try this code snipped below:

WorkItemStore workItemStore = teamProjectCollection.GetService<WorkItemStore>();
var workItem = workItemStore.GetWorkItem(testCaseId);
List<WorkItem> wilist = new List<WorkItem>();
foreach (WorkItemLink wiLink in workItem.WorkItemLinks)
{
    if (wiLink.LinkTypeEnd.Name.Equals("Tests"))
    {
                    int targetId = wiLink.TargetId;
                    var linkedWI = workItemStore.GetWorkItem(targetId);
                    if (linkedWI.Fields["Work Item Type"].Value.ToString() == "User Story")
                    {
                        wilist.Add(linkedWI);   // Add the user story to the list                        
                    }
    }
}

You could also use this TFS REST API:

GET  http://serverName:8080/tfs/DefaultCollection/_apis/wit/workitems/309?$expand=relations&api-version=1.0

About using it in C#, please refer to: https://www.visualstudio.com/en-us/docs/integrate/api/wit/work-items#with-links-and-attachments-1