循环遍历数据表并删除行

Question

I have populated a Datatable, from 2 different servers. I am able to make adjustments where my length>0, what I want to do is remove the rows that does not hit. Here is a summary of what I have

DataRow[] dr = payments.dtPayments.Select(myselect);

if (dr.Length > 0)
{
   for (int a = 0; a < dr.Length; a++)
   {
      if (thisOption == true)
         dr[0].Delete();
      else if (otherOption == true)
      {
         dr[0]["Date"] = myDataReader["date"].ToString().Trim();
         dr[0]["Pay"] = payTypeName(myDataReader["ccdsrc"].ToString()
                                                          .Trim());
      }
   }
}
if (dr.Length == 0)
{                        
   if (LastOption == true)
   {
     //DataRow should be removed
   }                        
}

Answer 1

I'm not sure I completely understand your question but it seems that you try to remove an entry from the collection while you are still looping over it. (which will cause an array index error)

You should save a reference to each entry you want to delete in a new collection and then remove all the new entries from the old collection:

DataRow[] dr = payments.dtPayments.Select(myselect);
List<DataRow> rowsToRemove = new List<DataRow>();

for (int a = 0; a < dr.Length; a++) {
    if(/* You want to delete this row */) {
        rowsToRemove.Add(dr[a]);
    }
}

foreach(var dr in rowsToRemove) {
    payments.dtPayments.Rows.Remove(dr);
}

Answer 2

If dr.Length is zero, then your select did not return any rows. If you want to delete rows that don't match your criteria, then I would implement that as a different type of query. It could also be that I am completely misunderstanding your question. Could you update your question to show your SQL and indicate where in the code sample you are having the problem: inside the loop or after the loop where you have your comment?

Answer 3

You need to create a datarow outside the loop, then when you get to the row you want to remove assign it to the row you created outside. and break the loop. Then below the loop you can remove it.

DataRow r = null;
foreach(DataRow row in table.Rows)
{
   if(condition==true)
   {
      r = row;
      break;
   }
}

table.Rows.Remove(r);

Answer 4

Have you tryed this?

payments.dtPayments.Rows.Remove(dr)

Answer 5

您可以反向循环遍历集合（对于（int i = rows.length-1; x> -1; x--））以删除多行，以确保您不会获得索引超出绑定的错误。