Overwriting existing data in an Excel worksheet using ADO.Net
 

Hi,

I'm wanting to write an in memory ADO.Net Datatable to a
worksheet
in an Excel spreadsheet. If the worksheet exists I would like to
overwrite all the existing data in the worksheet.

I've successfully used the Jet OLE DB Provider to create a new Excel
worksheet (using a CREATE TABLE) and populate it. But I haven't been
able to overwrite data in an existing worksheet.

In an old posting (Oct 2002) to microsoft.public.data.ado (Subject:
Delete records in Excel with ADO from VB) it was mentioned that Excel
automation is needed to delete empty rows cleanly. But it also
mentioned
that you can execute a DROP TABLE and start over.

I have tried using DROP TABLE which deletes all the data in a worksheet,
however it also seems to delete the column headers which means when I
use the InsertCommand on an OleDbDataAdapter to write the dataTable to
Excel no data gets written.

I was hoping DROP TABLE would actually delete the worksheet (rather than
just it's contents) so that I could then re-create the worksheet (using
CREATE TABLE).

Question :
------------
Am I doing something wrong with my InsertCommand, or is there some way
I can delete the worksheet itself or delete the contents of the
worksheet and still leave the column headers intact ?

I would like to avoid using Excel automation if possible, since if I
don't use it Excel does not need to be installed, versioning issues can
be avoided and I presume that using the Jet OLE DB Provider is faster
than using automation.

Thanks in advance,
Joel Gordon.

Overwriting existing data in an Excel worksheet using ADO.Net
 

Hi

Because Excel workbook did not have primary key, so the DELETE command is
not support.
Based on my test, after we call the drop table to delete the content from
the worksheet, we still can call the create table to recreate table.
private void button1_Click(object sender, System.EventArgs e)
{
// Establish a connection to the data source.
System.Data.OleDb.OleDbConnection objConn = new
System.Data.OleDb.OleDbConnection(
@"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=Book1.xls;Extended
Properties=Excel 8.0;Persist Security Info=False");
objConn.Open();

// Add two records to the table named 'MyTable'.
System.Data.OleDb.OleDbCommand objCmd = new
System.Data.OleDb.OleDbCommand();
objCmd.Connection = objConn;

objCmd.CommandText = "CREATE TABLE Test(x INT,y varchar(50))";
objCmd.ExecuteNonQuery();
objCmd.CommandText = "INSERT INTO Test VALUES (2,'Hello')";
objCmd.ExecuteNonQuery();
objCmd.CommandText = "INSERT INTO Test VALUES (3,'Test')";
objCmd.ExecuteNonQuery();

objCmd.CommandText = "drop table Test";
objCmd.ExecuteNonQuery();


objCmd.CommandText = "CREATE TABLE Test(x INT,y varchar(50))";
objCmd.ExecuteNonQuery();
objCmd.CommandText = "INSERT INTO Test VALUES (4,'Hello')";
objCmd.ExecuteNonQuery();
objCmd.CommandText = "INSERT INTO Test VALUES (5,'Test')";
objCmd.ExecuteNonQuery();

// Close the connection.
objConn.Close();
}

You may take a look and let me know the result.

Best regards,

Peter Huang
Microsoft Online Partner Support

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Overwriting existing data in an Excel worksheet using ADO.Net
 

Overwriting existing data in an Excel worksheet using ADO.Net
 

Yes, Delete is not supported in JET for Excel file and Text file. They are
different from Access database file for storage. As you said, row
position/order matter this

For the original question, I think the best pratice is to drop the table
and create it again.

Luke