How to Foreach and assign values in multiple case conditions in C#?

Question

I have following cases and conditions:

I need to loop through some testCases (passed/failed)check and certify one key. Basicaly i am checking some testcases and key validation

Case 1- All test cases execute and pass, certificate key found and certified

Result-test cases found. All test cases passed.Data  certified.

Case 2- Some or all test cases failed, certificate key found and certified

Result-

WARNING: test cases found. The following test test cases failed:
Test case ID '1'
Test case ID '123'
Test case ID '4223'
Test case ID '321'
 Data  certified.

Case 3- Some/all test cases failed, certificate key NOT found

Result -

WARNING: test cases found. The following test test cases failed:
Test case ID '1'
Test case ID '123'
Test case ID '4223'
Test case ID '321'
WARNING: No  data certificate key found,  data  not certified'

Case 4 – All test cases execute and pass, certificate key found and NOT certified

Result -

test cases found. All test cases passed.
WARNING: data certificate key found, Certification key not valid,  data  not certified'

1.KEY CAN BE NULL
2.KEY CAN BE THERE BUT NOT THE EXACT KEY 
3.KEY IS THERE,EXACT ONE-CERTIFIED
4.TEST RESULT WILL BE PASSED OR FAILED

How can i loop through all these conditions and assign values and error messages based on this loop?

WHAT I HAVE TRIED AND STUCK:

public Task GetTestResults(string infoset){
    
    //getting "resultDataSet" from DB
     
    var table = resultDataSet.Tables[0];
    var results = table
                        .Rows
                        .Cast()
                        ?.Select(x => new ResultModel
                        {
                            TestCases = x["TestCases"] as string,
                            Message = x["ErrorMessage"] as string,
                            ResultStatus = x["ResultStatus"] as string,
                            DataKey = x["ValidationKey"] as string,
                            TestType = x["TestType"] as string
                        });

                           // TestCases = array of multiple test cases
                           // Message =error  msg based on case we have to add
                           // ResultStatus =Passed or Failed in test cases
                         //   DataKey =some key like 4252634343567TSA
                           // TestType =smoke/unit test

               bool isValidKey = await _Ichekkey.IsValidcertificateKey(string key)
    int testCasesCount = Convert.ToInt32(table.Rows[0]["TestCases"]);
    bool keyFound;
    bool alltcPassed;
    foreach (var data in results)
    {
        if (!String.IsNullOrEmpty(data.DataKey))
        {
           keyFound = true;
           List FailedTestCases = new List();
           if (data.ResultStatus == "Failed")
           {
               FailedTestCases.Add(data.TestCases);
           }

           if (FailedTestCases.Count > 0)
           {
               alltcPassed = false;
           }
           else
           {
               // passed
               alltcPassed = true;
           }
        }

        // blocked here confused to continue to check and assign the case results and messages       
    }
    return result;
}

Can anyone help me? Thanks in advance...