以相反顺序循环数据集

Question

I have a dataset with say 1 to 'n' number of DataTables in it and I want to loop it but in the reverse order ie, from DataTable n to DataTable 1 . Can anyone suggest me a way to do this. I found some solutions but all are for sorting DataTables not Datasets.

DataSet _ds = new DataSet();
foreach (DataTable table in _ds.Tables)
{

}

Answer 1

You could use LINQ, you need to cast it because DataTableCollection doesn't implement IEnumerable<DataTable> but only the non-generic IEnumerable interface:

var reversedTables = _ds.Tables.Cast<DataTable>().Reverse();
foreach(DataTable table in reversedTables)
{
    // ...
}

or with a plain for -loop:

for (int i = _ds.Tables.Count - 1; i >= 0; i--)
{
    DataTable table = _ds.Tables[i];
     // ...
}

Answer 2

you can use a for-loop instead:

DataSet _ds = new DataSet();
for (int i=_ds.Tables.Count-1; i>=0; i--)
{
   DataTable table = _ds.Tables[i];
}

Answer 3

or even simpler by decrement i within the array indexer accessor :

DataSet _ds = new DataSet();
for (int i=_ds.Tables.Count-1; i>=0; )
{
   DataTable table = _ds.Tables[i--];
}

or by using a while-loop doing the same:

int i=_ds.Tables.Count;
while (i>=0)
{
    DataTable table = _ds.Tables[i--];
};