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.NET Forum / ASP.NET / General / February 2008Dataset not Clearing
I am trying to clear my dataset each time I read a new csv file but it seems to keep the data from the previous time. If I do: ******************************************************************************** foreach (string strFile in strFiles) { ds.Clear(); da = new OleDbDataAdapter("SELECT * FROM " + Path.GetFileName(strFile),csvConnection); da.Fill(ds); foreach (DataTable dt in ds.Tables) { for (int i=0;i<dt.Columns.Count-1;i++) { switch(i) { case 0: formName = dt.Columns[i].ColumnName.Replace("Form ",""); dt.Columns[i].ColumnName = "FieldName"; break; ********************************************************************************* The second time I read a file (after the ds.Clear();) I find that my dt.Columns[i].ColumnName will be equal to "FieldName", which is what I change the column to the first time around!!! Why is that? It should be what is in the first row, first column of the table, since I wiped out the table. If not, how do I get it to work correctly? Thanks, Tom Hello tshad, Seems that it's code optimization :) Try to trace the dataSet content after clearing it in release mode. Because I assume that in debug it just don't clear it when u ask and keep it till u either override it or exit the function --- WBR, Michael Nemtsev [.NET/C# MVP] :: blog: http://spaces.live.com/laflour "The greatest danger for most of us is not that our aim is too high and we miss it, but that it is too low and we reach it" (c) Michelangelo t> I am trying to clear my dataset each time I read a new csv file but t> it seems to keep the data from the previous time. t> t> If I do: t> ********************************************************************* t> *********** t> foreach (string strFile in strFiles) t> { t> ds.Clear(); t> da = new OleDbDataAdapter("SELECT * FROM " + t> Path.GetFileName(strFile),csvConnection); t> da.Fill(ds); t> foreach (DataTable dt in ds.Tables) t> { t> for (int i=0;i<dt.Columns.Count-1;i++) t> { t> switch(i) t> { t> case 0: t> formName = dt.Columns[i].ColumnName.Replace("Form ",""); t> dt.Columns[i].ColumnName = "FieldName"; t> break; t> ********************************************************************* t> ************ t> The second time I read a file (after the ds.Clear();) I find that my t> dt.Columns[i].ColumnName will be equal to "FieldName", which is what t> I change the column to the first time around!!! t> t> Why is that? t> t> It should be what is in the first row, first column of the table, t> since I wiped out the table. If not, how do I get it to work t> correctly? t> t> Thanks, t> t> Tom t> > Hello tshad, > > Seems that it's code optimization :) > Try to trace the dataSet content after clearing it in release mode. > Because I assume that in debug it just don't clear it when u ask and keep > it till u either override it or exit the function That doesn't appear to be the case, because it is getting cleared. Only the column names are not getting cleared. If I trace it through, before my da.Fill() I get: ds.Tables[0].Rows[0][0] 'ds.Tables[0]' threw an exception of type 'System.IndexOutOfRangeException' object {System.IndexOutOfRangeException} This is the same on both passes (which is expected). For column names it is the same: ds.Tables[0].Columns[0].ColumnName 'ds.Tables[0]' threw an exception of type 'System.IndexOutOfRangeException' string {System.IndexOutOfRangeException} But it is only the same on the first pass. On the second pass, the rows show as out of range, but the column names are the same as I set them on the first pass. The problem is that on the first pass, the column names are what is in the 1st column of row 0 of the csv file (which is what I want). But on the 2nd pass, it stays what I changed it to and never picks up the 1st column of the 2nd file. The problem is that this column tells me what type of file I am dealing with. Why doesn't it read the first column here? My connection string says to use the headers from the 1st row, which it does on the first file: OleDbConnection csvConnection = new OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + csvPath + ";Extended Properties=\"Text;HDR=Yes;FMT=Delimited\""); "HDR=Yes;" Thanks, Tom > --- > WBR, Michael Nemtsev [.NET/C# MVP] :: blog: [quoted text clipped - 35 lines] > t> t> Tom > t> >> Hello tshad, >> [quoted text clipped - 6 lines] > > Only the column names are not getting cleared. I found out how to make it work, I just don't know why I would have to do this: If I add ds.tables.clear() after ds.clear(), this will clear the column names as well. This doesn't make sense to me as I would have thought that ds.clear (which gets rid of the tables) would also get rid of the columns names for the tables which now don't exist. Thanks, Tom > If I trace it through, before my da.Fill() I get: > ds.Tables[0].Rows[0][0] 'ds.Tables[0]' threw an exception of type [quoted text clipped - 71 lines] >> t> t> Tom >> t> >>> Hello tshad, >>> [quoted text clipped - 6 lines] >> >> Only the column names are not getting cleared. Also, after the ds.Clear(), even though there is no table data (rows[0][0] will give a System.IndexOutOfRangeException), ds.Tables.Count still shows as 1. So certain things are cleared from the ds as well as certain table information, but not all of it. I found that I can do: ds.Tables.Clear() And that seems to clear everything. I say "SEEMS TO" because I am not sure if there are other things that don't get cleared but haven't run into them yet. It may be that you need to issue both. I would like to see what each does clear just to make sure, but I can't seem to find anything about it. Thanks, Tom > I found out how to make it work, I just don't know why I would have to do > this: [quoted text clipped - 86 lines] >>> t> t> Tom >>> t> Hello tshad, Actually in should call the .clear for all tables inside the data set. if u take reflector you found the code, which iterate all table collection and call clear for tables --- WBR, Michael Nemtsev [.NET/C# MVP] :: blog: http://spaces.live.com/laflour "The greatest danger for most of us is not that our aim is too high and we miss it, but that it is too low and we reach it" (c) Michelangelo t> "tshad" <tfs@dslextreme.com> wrote in message t> news:OXe9LtYbIHA.4712@TK2MSFTNGP04.phx.gbl... t> >>> Hello tshad, >>> [quoted text clipped - 6 lines] >> >> Only the column names are not getting cleared. t> I found out how to make it work, I just don't know why I would have t> to do this: t> t> If I add ds.tables.clear() after ds.clear(), this will clear the t> column names as well. t> t> This doesn't make sense to me as I would have thought that ds.clear t> (which gets rid of the tables) would also get rid of the columns t> names for the tables which now don't exist. t> t> Thanks, t> t> Tom t> >> If I trace it through, before my da.Fill() I get: >> ds.Tables[0].Rows[0][0] 'ds.Tables[0]' threw an exception of [quoted text clipped - 80 lines] >>> t> t> Tom >>> t> > Hello tshad, > > Actually in should call the .clear for all tables inside the data set. > if u take reflector you found the code, which iterate all table collection > and call clear for tables Not sure what you mean here. ds.clear() does clear all the tables, just not the columnname and ds.tables.count(). ds.Tables.Clear() appears to clear all the tables including the columnNames and ds.tables.count(). I am just not sure if I should call both. There may be something that ds.clear() handles that ds.tables.clear() doesn't (just like the problem when I do the reverse). Thanks, Tom > --- > WBR, Michael Nemtsev [.NET/C# MVP] :: blog: [quoted text clipped - 111 lines] >>>> t> t> Tom >>>> t> > Hello tshad, > > Actually in should call the .clear for all tables inside the data set. > if u take reflector you found the code, which iterate all table collection > and call clear for tables Not sure what you mean by this? Are you saying that you need to do a foreach loop and clear each table? Thanks, Tom > --- > WBR, Michael Nemtsev [.NET/C# MVP] :: blog: [quoted text clipped - 111 lines] >>>> t> t> Tom >>>> t> Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
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