Develop Reference

Delete multiple rows from DatagridView (Transfer to Subtable)

I am writing a code where I transfer rows between two datagridiews. The rows I selected are transferred to the sub table and I want the transferred rows to be deleted from the table above. However, with this code I wrote, only the last row is deleted from the table, but all of them are transferred to the table below. here is my codes
if (dataGridView1.SelectedRows.Count == dataGridView1.Rows.Count)
{
dataGridView1.Rows.Clear();
}
foreach (DataGridViewRow row in dataGridView1.SelectedRows)
{
dataGridView1.Rows.Remove(row);
}
where is my mistake?
can you help me?

Update :Result is not transfered to the orginal dataset. Sorting Rows in Dataset using C#

Update: even though I have got the required result but when the the second function access the data table the value is still the same
It a sequential program with two functions in different classes. First sort and second replace function. So it should sort the value and other function should be able to retrieve the sorted table but when it retrieve the datatable it gives the unsorted table.
I have used acceptchanges() but it also give the same result.
The program is trying to sort the table according to the required field and the result is stored in Sorted table variable. I am trying to copy this to the original i-e sourceTables but it is not working and is adding another row instead of updating [As shown in below dig]. I have tried to copy whole table but it does not work and by adding rows it is not giving the required result. I have used different methods but I am not getting the required result.
List<DataTable> sourceTables = context.GetDataByTable(sourceTable.StringValue);
List<DataTable> targetTables = context.GetDataByTable(targetTable.StringValue, sourceTables.Count);
string orderDesc= orderField.StringValue + " DESC";
for (int i = 0; i < sourceTables.Count; i++)
{
DataView dv = sourceTables[i].DefaultView;
if (orderDirection.StringValue == OrderDirectionAsc)
{
// for Sorting in Ascending Order
dv.Sort = orderField.StringValue;
}
else
{
// for Sorting in Descending Order
dv.Sort = orderDesc;
}
DataTable sortedTable = dv.ToTable();
DataTable dttableNew = sortedTable.Clone();
//sourceTables[i] = sortedTable.Copy();
//targetTables[i] = dv.ToTable();
//targetTables[i] = sortedTable.Copy();
// foreach (DataRow dr in sortedTable.Rows)
//// targetTables[i].Rows.Add(dr.ItemArray);
//}
for (int j = 0; j < sourceTables[i].Rows.Count; j++)
{
if (sourceTable.GetValue().ToString() == targetTable.GetValue().ToString())
{
foreach (DataRow dr in sortedTable.Rows)
{
targetTables[i].Rows.Add(dr.ItemArray);
}
else
{
foreach (DataRow dr in sortedTable.Rows)
{
targetTables[i].Rows.Add(dr.ItemArray);
}
// targetTables[i] = sortedTable.Copy(); does not work
//foreach (DataRow drtableOld in sortedTable.Rows)
//{
// targetTables[i].ImportRow(drtableOld);
//}
Instead of replacing the first values it is adding more rows
any help would be appreciated

If any one have problem with duplicate data or the changes are only local and is not effecting the original data table. Remember to always use .ImportRow(dr) function to add rows to the table and if you use Tables[i].Rows.Add(dr.ItemArray); the changes will affect only the local table and not the original one. Use .clear to remove the old rows from the orginal table. The action done directly on the original function will only effect the rows. If it is done on the clone copy changes will nor affect the original table.
Here is the complete code
DataTable sortTable = dv.ToTable();
if (sTable.GetValue().ToString() == tTable.GetValue().ToString())
{
sTables[i].Clear();
foreach (DataRow dr in sortTable.Rows)
{
sTables[i].ImportRow(dr);
}
sTables[i].AcceptChanges();
}

GetChanges from merged datatables returns null

I have following code:
DataTable datTable3 = new DataTable();
datTable3 = datTable1.Clone();
datTable2.Merge(datTable1);
datTable3 = datTable2.GetChanges();
Want I want to do is: Compare DataTable1 with DataTable2 and when there are rows in DataTable1 which aren't in DataTable 2 then add these rows into a new DataTable(3). This code above gives me an empty DataTable3 each time although the rows in the first dt are not equal to the rows in my second dt. what am I doing wrong? Sorry if that question may be too easy but I'm using C# since a couple of months.
EDIT: I found this solution which doesn't work for me... Why?
DataTable datTable3 = new DataTable();
datTable3 = datTable1.Clone();
foreach (DataRow row in datTable1.Rows)
{
datTable3.ImportRow(row);
}
foreach (DataRow row in datTable3.Rows)
{
row.SetAdded();
}
datTable2.Merge(datTable3);
DataTable datTableFinal = datTable2.GetChanges(DataRowState.Added);
// shows me a datatable with again the values from datTable1
// even if they are already in datTable2!
datTable2.RejectChanges();
datTable1.RejectChanges();

The DataTable.GetChanges() method Gets a copy of the DataTable that contains all changes made to it since it was loaded or AcceptChanges was last called.
In other words, GetChanges() is dependent on the DataRow.RowState property. A DataTable.Merge() will either preserve their 'RowState' property, or reset it to 'Unchanged'.
This means that when you merge two DataTables with rows that have 'Unchanged' RowStates, the merged table will also contain 'Unchanged' rows and the DataTable.GetChanges method will return null or Nothing.
EDIT : You can always iterate through the DataTable to see what rows are added to the merged table. Something like
foreach(DataRow row in datTable2.Rows)
{
Console.WriteLine("--- Row ---"); // Print separator.
foreach (var item in row.ItemArray) // Loop over the items.
{
Console.Write("Item: "); // Print label.
Console.WriteLine(item); // Invokes ToString abstract method.
}
}

Iterate through and use LoadDataRow(object[] value, bool fAcceptChanges) :
foreach (DataRow row in MergeTable.Rows)
{
TargetTable.LoadDataRow(row.ItemArray, false);
}
var changes = TargetTable.GetChanges();
changes had the desired value when I tried this method.

Delete row from datatable where first column does not contain (some string)

I have DataTable with the following columns:
ClientID date numberOfTransactions price
ClientID is of type string and I need to ensure that its contents include "A-" and "N6" for every value in the table.
I need to delete all rows from the DataTable where this first column (ClientID) does not contain both "A-" and "N6" (some totals and other unnecessary data). How can I select and delete these rows specifically from the DataTable?
I know this:
foreach (DataRow row in table.Rows) // Loop over the rows.
{
//Here should come part "if first column contains mentioned values
}
I also know this
If (string.Contains("A-") == true && string.Contains("N6") == true)
{
//Do something
}
I need help how to implement this for first column of each row.

Try this:
EDIT: Totally messed up that last line, so if you tried it, try it now that I made it not stupid. =)
List<int> IndicesToRemove = new List<int>();
DataTable table = new DataTable(); //Obviously, your table will already exist at this point
foreach (DataRow row in table.Rows)
{
if (!(row["ClientID"].ToString().Contains("A-") && row["ClientID"].ToString().Contains("N6")))
IndicesToRemove.Add(table.Rows.IndexOf(row));
}
IndicesToRemove.Sort();
for (int i = IndicesToRemove.Count - 1; i >= 0; i--) table.Rows.RemoveAt(IndicesToRemove[i]);

try using this,
assuming dt as your Datatabe object and ClientID as your first column (hence using ItemArray[0])
for(int i=0; i<dt.Rows.Count; i++)
{
temp = dt.Rows[i].ItemArray[0].ToString();
if (System.Text.RegularExpressions.Regex.IsMatch(temp, "A-", System.Text.RegularExpressions.RegexOptions.IgnoreCase) || System.Text.RegularExpressions.Regex.IsMatch(temp, "N6", System.Text.RegularExpressions.RegexOptions.IgnoreCase))
{
dt.Rows.RemoveAt(i);
i--;
}
}
Simple and straight forward solution... hope it helps

this should be more efficient, both in lines of Code and Time, try this :)
for(int x=0; x<table.Rows.Count;)
{
if (!table.Rows[x].ItemArray[0].contains("A-") && !table.Rows[x].ItemArray[0].contains("N6"))
table.Rows.RemoveAt(x);
else x++;
}
Happy Coding

Preface: C.Barlow's existing answer is awesome, this is just another route someone could take.
This is one way to do it where you never have to loop all the way through the original table (by taking advantage of the DataTable.Select() method):
DataTable table = new DataTable(); // This would be your existing DataTable
// Grab only the rows that meet your criteria using the .Select() method
DataRow[] newRows = table.Select("ClientID LIKE '%A-%' AND ClientID LIKE '%N6%'");
// Create a new table with the same schema as your existing one.
DataTable newTable = table.Clone();
foreach (DataRow r in newRows)
{
// Dump the selected rows into the table.
newTable.LoadDataRow(r.ItemArray, true);
}
And now you have a DataTable with only the rows you want. If necessary, at this point you could clear out the original table and replace it with the contents of the new one:
table.Clear();
table = newTable.Copy();
Edit: I thought of a memory optimization last night, you can just overwrite the existing table once you have the rows you need, which avoids the need for the temporary table.
DataTable table = new DataTable(); // This would be your existing DataTable
// Grab only the rows that meet your criteria using the .Select() method
DataRow[] newRows = table.Select("ClientID LIKE '%A-%' AND ClientID LIKE '%N6%'");
// Clear out the old table
table.Clear();
foreach (DataRow r in newRows)
{
// Dump the selected rows into the table.
table.LoadDataRow(r.ItemArray, true);
}

How to delete all rows from datatable

I want to delete all rows from datatable with rowstate property value Deleted.
DataTable dt;
dt.Clear(); // this will not set rowstate property to delete.
Currently I am iterating through all rows and deleting each row.
Is there any efficient way?
I don't want to delete in SQL Server I want to use DataTable method.

We are using this way:
for(int i = table.Rows.Count - 1; i >= 0; i--) {
DataRow row = table.Rows[i];
if ( row.RowState == DataRowState.Deleted ) { table.Rows.RemoveAt(i); }
}

This will satisfy any FK cascade relationships, like 'delete' (that DataTable.Clear() will not):
DataTable dt = ...;
// Remove all
while(dt.Count > 0)
{
dt.Rows[0].Delete();
}

dt.Rows.Clear();
dt.Columns.Clear(); //warning: All Columns delete
dt.Dispose();

I typically execute the following SQL command:
DELETE FROM TABLE WHERE ID>0

Since you're using an SQL Server database, I would advocate simply executing the SQL command "DELETE FROM " + dt.TableName.

I would drop the table, fastest way to delete everything. Then recreate the table.

You could create a stored procedure on the SQL Server db that deletes all the rows in the table, execute it from your C# code, then requery the datatable.

Here is the solution that I settled on in my own code after searching for this question, taking inspiration from Jorge's answer.
DataTable RemoveRowsTable = ...;
int i=0;
//Remove All
while (i < RemoveRowsTable.Rows.Count)
{
DataRow currentRow = RemoveRowsTable.Rows[i];
if (currentRow.RowState != DataRowState.Deleted)
{
currentRow.Delete();
}
else
{
i++;
}
}
This way, you ensure all rows either get deleted, or have their DataRowState set to Deleted.
Also, you won't get the InvalidOperationException due to modifying a collection while enumerating, because foreach isn't used. However, the infinite loop bug that Jorge's solution is vulnerable to isn't a problem here because the code will increment past a DataRow whose DataRowState has already been set to Deleted.