Another question today. This time, I'm having trouble deleting a row from a SQL Server CE database.
private void Form1_Load(object sender, EventArgs e)
{
// Create a connection to the file datafile.sdf in the program folder
string dbfile = new System.IO.FileInfo(System.Reflection.Assembly.GetExecutingAssembly().Location).DirectoryName + "\\userDtbs.sdf";
SqlCeConnection connection = new SqlCeConnection("datasource=" + dbfile);
// Read all rows from the table test_table into a dataset (note, the adapter automatically opens the connection)
SqlCeDataAdapter adapter = new SqlCeDataAdapter("SELECT * FROM history", connection);
DataSet data = new DataSet();
adapter.Fill(data);
//Delete from the database
using (SqlCeCommand com = new SqlCeCommand("DELETE FROM accounts WHERE Id = 0", connection))
{
com.ExecuteNonQuery();
}
// Save data back to the databasefile
var cmd = new SqlCeCommandBuilder(adapter);
adapter.Update(data);
// Close
connection.Close();
}
My program's giving me an error telling me that connection
is in a closed state, and I can't figure out why it would close before the DELETE
command is executed.
Note that: executing command with Command.ExecuteXXX()
requires the connection to be open first. Filling data into DataSet
using SqlDataAdapter.Fill
doesn't require that because it handles that internally. Executing the SQL query
this way is direct and don't require any Update
method call on adapter
(as you add in your code after deleting). Update
is just for saving changes made on your DataSet
.
//Delete from the database
using (SqlCeCommand com = new SqlCeCommand("DELETE FROM accounts WHERE Id = 0", connection))
{
if(connection.State == ConnectionState.Closed) connection.Open();
com.ExecuteNonQuery();
}
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.