C# How to update variable value in a loop

Question

Hi expert, I've try to loop and from the below code, The problem is when it loop back to “IEnumerable selectedRows =”. The value of DateStart and DateEnd remain the same “9/1/2003 2:00:00” and “9/1/2003 2:59:00” respectively as its initial value. Why the “IEnumerable selectedRows =” do not update the DateTime value? Please help and thank you.

Below is the code;

DateTime DateStart = Convert.ToDateTime("9/1/2023 2:00:00");  
DateTime DateEnd = DateStart + TimeSpan.FromMinutes(59);  
  
for (int intCount=0; intCount < 8; intCount++)  
{  
                      
    IEnumerable<DataRow> selectedRows = dtData.AsEnumerable().Where(row => (row.Field<DateTime>("Date") >= DateStart) && row.Field<DateTime>("Date") <= DateEnd);  
  
  
      foreach (DataRow row in selectedRows)  
      {  
    
         //Do some stuffs  
  
      }  
        
      //store the result in DataTable  
      DataRow dtDataRowResult = dtDataResult.NewRow();  
      dtDataRowResult[0] = DateStart;  
      dtDataRowResult[1] = result1;  
      dtDataRowResult[2] = result2;  
      dtDataResult.Rows.Add(dtDataRowResult);  
  
      //when code go this line below, it should be added one hour from the previous hour, so now it is “9/1/2003 3:00:00”  
      DateStart = DateStart.AddHours(1);  
     //and the DateEnd should be added to “9/1/2003 3:59:00”  
      DateEnd = DateStart + TimeSpan.FromMinutes(59);  
     //The problem is when it loop back to “IEnumerable<DataRow> selectedRows =”. The value of DateStart and DateEnd remain the same “9/1/2003 2:00:00” and “9/1/2003 2:59:00” respectively as the initial value. Why the “IEnumerable<DataRow> selectedRows =” do not updated the DateTime value? Please help and thank you.  
  

The below is the screenshot image of the example code;

Answer 1

I've done in console app, everything is works properly and I apply this code to my previous code, it works properly. Anyway thanks.

Below is the example of the code.

static void Main(string[] args)  
        {  
            DataTable dtDataResult = new DataTable();  
            DataColumn dcDataResult = dtDataResult.Columns.Add("DateTime", typeof(DateTime));  
            dcDataResult = dtDataResult.Columns.Add("Count", typeof(Int16));  
  
            DateTime DateStart = Convert.ToDateTime("9/1/2023 2:00:00");  
            DateTime DateEnd = DateStart + TimeSpan.FromMinutes(59);  
  
            for (int intCount = 0; intCount < 8; intCount++)  
            {  
                int intTest = 0;  
                TimeSpan tsGetHours = DateEnd - DateStart;  
  
                for (int intDataRow=0; intDataRow< 10; intDataRow++)  
                {  
                    intTest++;  
  
                }  
                DataRow dtDataRowResult = dtDataResult.NewRow();  
                dtDataRowResult[0] = DateStart;  
                dtDataRowResult[1] = intTest;  
                dtDataResult.Rows.Add(dtDataRowResult);  
  
                DateStart = DateStart.AddHours(1);  
                DateEnd = DateStart + TimeSpan.FromMinutes(59);  
  
            }  
  
        }  

below is the screenshot image of the code.