How to Solve this Error "Cannot convert lambda expression to type 'string' because it is not a delegate type"

Question

. I get this error: "Cannot convert lambda expression to type 'string' because it is not a delegate type" - keyword select become underlined in blue Can you please advice.

   Employee emp = new Employee();
   comHandledBySQt.DataSource = from x in emp.GetDataFromTable("1")
                    select new { x.Id, Name = x.FirstName + " " + x.LastName };
   comHandledBySQt.DisplayMember = "Name";
   comHandledBySQt.ValueMember = "Id";

Above code should displays drop list of employees first name and last name in a combo box

Answer 1

x.Id might need to be made an assignment, eg.
select new { Id = x.Id, Name = string.Format("{0} {1}", x.FirstName, x.LastName) };

DataSet is not enumerable, so if GetDataFromTable("1") returns DataSet, you need to enumerate over the appropriate result set / table, eg. GetDataFromTable("1").Tables[0] if you only have one result set.

Each element in the enumeration will then be a DataRow, which has an index (rather than property) accessor: DataRow[columnIndex] or DataRow[columnName].

Answer 2

If you have a strongly typed dataset, you can absolutely perform a query on the named members of a table in a manner close to what you have tried.

var queryA = (from x in dataSet.EmployeeTable
                        select new { x.Id, Name = x.FirstName + " " + x.LastName }).ToList();

From your given error, it does not appear that you have a strongly-type dataset, and it could very well be that your return value is not a DataSet but rather just a DataTable (at least, from my attempts at recreating your error message, I was getting it on the DataTable and not the set). But without a strongly-typed DataSet/DataTable, this is the query you would perform.

var queryB = (from DataRow x in someSet.Tables[0].Rows
            select new { Id = (string)x["Id"], Name = (string)x["FirstName"] + " " + (string)x["LastName"] }).ToList();

Notice that in both instances you would include a .ToList() call, as without it you get another error saying that the complex databinding requires an IList or IListSource, which the query (without the ToList() call) is neither.