List of Task working in parallel but not getting Result

Question

List of Task working in parallel but not getting Result ,,Throwing exception .

var listTask = new List<Task>();
                if (assessmentDatas.Count > 0) listTask.Add(Task.Factory.StartNew(() => BulkHelper.GetDataTable(assessmentDatas)));
                if (adLimits.Count > 0) listTask.Add(Task.Factory.StartNew(() => BulkHelper.GetDataTable(adLimits)));
                if (variables.Count > 0) listTask.Add(Task.Factory.StartNew(() => BulkHelper.GetDataTable(variables)));
                if (resultValues.Count > 0) listTask.Add(Task.Factory.StartNew(() => BulkHelper.GetDataTable(resultValues)));      
                 Task.WaitAll(listTask.ToArray());   

                var results = listTask.Select(x => ((Task<(DataTable dt, string tableName, string tempTableName, Type type)>)x).Result).ToList(); Exception Thrown here

Above Code is Working in Parallel but not able to Get Result.

Below Code I am getting Result, but Not Working in Parallel

  var listTask = new List<Task>();
            if (assessmentDatas.Count > 0) listTask.Add(Task.Factory.StartNew(() => BulkHelper.GetDataTable(assessmentDatas)).Result);
            if (adLimits.Count > 0) listTask.Add(Task.Factory.StartNew(() => BulkHelper.GetDataTable(adLimits)).Result);
            if (variables.Count > 0) listTask.Add(Task.Factory.StartNew(() => BulkHelper.GetDataTable(variables)).Result);
            if (resultValues.Count > 0) listTask.Add(Task.Factory.StartNew(() => BulkHelper.GetDataTable(resultValues)).Result);      

            Task.WaitAll(listTask.ToArray());

            var results = listTask.Select(x => ((Task<(DataTable dt, string tableName, string tempTableName, Type type)>)x).Result).ToList();

Answer 1

Hi,
change your code, please:

var listTask = new List<Task>();
if (assessmentDatas.Count > 0) listTask.Add(Task.Factory.StartNew(() => BulkHelper.GetDataTable(assessmentDatas)));
if (adLimits.Count > 0) listTask.Add(Task.Factory.StartNew(() => BulkHelper.GetDataTable(adLimits)));
if (variables.Count > 0) listTask.Add(Task.Factory.StartNew(() => BulkHelper.GetDataTable(variables)));
if (resultValues.Count > 0) listTask.Add(Task.Factory.StartNew(() => BulkHelper.GetDataTable(resultValues)));
Task.WaitAll(listTask.ToArray());

var results = listTask.Select(x => (Task<Task<(DataTable dt, string tableName, string tempTableName, Type type)>>)x).Select(y => y.Result).Select(z => z.Result).ToList();