I have a non empty datatable . What is the best way to add another column to it that has sequential numbering starting from 1.
I tried the following code. But did not work.
DataColumn dc = new DataColumn("Col1");
dc.AutoIncrement = true;
dc.AutoIncrementSeed = 1;
dc.AutoIncrementStep = 1;
dc.DataType = typeof(Int32);
dt.Columns.Add(dc);
Will setting any expression help in this scenario ?
Thanks in Advance
I think you could achieve that by using a 2nd "helper" data table that would contain just an auto-increment field and then you populate/merge it with the existing data, something like this:
DataTable dtIncremented = new DataTable(dt.TableName);
DataColumn dc = new DataColumn("Col1");
dc.AutoIncrement = true;
dc.AutoIncrementSeed = 1;
dc.AutoIncrementStep = 1;
dc.DataType = typeof(Int32);
dtIncremented.Columns.Add(dc);
dtIncremented.BeginLoadData();
DataTableReader dtReader = new DataTableReader(dt);
dtIncremented.Load(dtReader);
dtIncremented.EndLoadData();
And then you would just return dtIncremented table instead of the original dt. Not an elegant solution but should work.
below code worked for me
Code is Edited
// Added temp rows so that this solution can mimic actual requirement
DataTable dt = new DataTable();
DataColumn dc1 = new DataColumn("Col");
dt.Columns.Add(dc1);
for(int i=0;i<10;i++)
{
DataRow dr = dt.NewRow();
dr["Col"] = i.ToString();
dt.Rows.Add(dr);
}
// Added new column with Autoincrement,
DataColumn dc = new DataColumn("Col1");
dc.AutoIncrement = true;
dc.AutoIncrementSeed = 1;
dc.DataType = typeof(Int32);
// Handeled CollectionChanged event
dt.Columns.CollectionChanged += new CollectionChangeEventHandler(Columns_CollectionChanged);
dt.Columns.Add(dc);
// After column added demostratation
DataRow dr1 = dt.NewRow();
dt.Rows.Add(dr1);
void Columns_CollectionChanged(object sender, CollectionChangeEventArgs e)
{
DataColumn dc = (e.Element as DataColumn);
if (dc != null && dc.AutoIncrement)
{
long i = dc.AutoIncrementSeed;
foreach (DataRow drow in dc.Table.Rows)
{
drow[dc] = i;
i++;
}
}
}
You'll have to build a whole new datatable for this and manually deep-copy each row one by one from the old table to the new. Sorry.
来源:https://stackoverflow.com/questions/4310791/best-way-add-a-new-column-with-sequential-numbering-in-an-existing-data-table