You should be able to follow the example in the link provided.
Suppose your have a DataTable like this
DataTable dt = new DataTable();
dt.Columns.Add("UserID");
dt.Columns.Add("FullName");
dt.Columns.Add("DateBooked");
dt.Columns.Add("RoomQty");
dt.Columns.Add("NoofNights");
dt.Rows.Add(1, "John Doe", DateTime.Now.AddDays(-7).Date, 2, 3);
dt.Rows.Add(2, "Jack Sparrow", DateTime.Now.AddDays(-14).Date, 1, 1);
dt.Rows.Add(3, "Arthur Wilson", DateTime.Now.AddDays(-10).Date, 2, 2);
dt.Rows.Add(4, "Amy Jackson", DateTime.Now.AddDays(-5).Date, 4, 2);
dt.Rows.Add(5, "Tim Lee", DateTime.Now.AddDays(-1).Date, 1, 5);
dt.Rows.Add(2, "Jack Sparrow", DateTime.Now.AddDays(-5).Date, 3, 2);
and your input parameters are
int userInput = 2;
DateTime dateBooked = DateTime.Now.AddDays(-14).Date;
int roomQty = 1;
int noOfNights = 1;
You can get the 'FullName'
column value like this (provided you will have a single record based on your where conditions)
string FullName = (from DataRow dr in dt.Rows
where Convert.ToInt32(dr["UserID"]) == userInput &&
Convert.ToDateTime(dr["DateBooked"]) == dateBooked &&
Convert.ToInt32(dr["RoomQty"]) == roomQty &&
Convert.ToInt32(dr["NoofNights"]) == noOfNights
select (string)dr["FullName"]).FirstOrDefault();