Hi,
I am writing a app that must have the ability to :
- GUI should be seen on a web interface (Thus I'm using C# Web Application)
- Be able to select .mdb files
- Add rows
- Delete rows
- Edit rows
- Save everything back to the .mdb file.
I have googled for ages.
I have written a similar application in a normal C# windows form application, I used OLEdb to do everything and it worked fine, it wasn't restricted to only one .mdb file.
In the C# Windows Form app I used Gridview control.
As the Web Application doesn't have Gridview, I used a datagrid.
Here is the code is have so far :
public partial class _Default : System.Web.UI.Page
{
string databasePath = "____________.mdb";
DataTable userTable = new DataTable();
OleDbDataAdapter adapter;
OleDbConnection connection;
OleDbCommand command;
OleDbCommandBuilder builder;
DataSet ds;
DataSet tempDs;
public string DatabaseName = null;
string connectionString = "Provider=Microsoft.Jet.OLEDB.4.0; Data Source=";
protected void Page_Load(object sender, EventArgs e)
{
tbDatabasePath.Text = databasePath;
}
protected void btnLoadData_Click(object sender, EventArgs e)
{
ReadRecords();
}
protected void btnGetTables_Click(object sender, EventArgs e)
{
try
{
ddTables.Items.Clear();
ddTables.Text = null;
getTables();
}
catch (Exception ex)
{
ClientScript.RegisterStartupScript(this.GetType(), "myalert", "alert('Could not retrieve the Tables');", true);
}
}
private void getTables()
{
string tempstring = "";
string getTConnection = connectionString + databasePath; ;
OleDbConnection myConnection = new OleDbConnection(getTConnection);
myConnection.Open();
DataTable datT = myConnection.GetSchema("Tables");
for (int i = 0; i < datT.Rows.Count; i++)
{
tempstring = datT.Rows[i][2].ToString();
if (tempstring.Contains("MSys"))
{
}
else
{
ddTables.Items.Add(datT.Rows[i][2].ToString());
}
}
myConnection.Close();
}
private void ReadRecords()
{
datagrid.DataSource = null;
OleDbDataReader reader = null;
try
{
connection = new OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0; " + "Data Source=" + databasePath);
OleDbCommand cmd = new OleDbCommand("Select * FROM " + ddTables.Text, connection);
adapter = new OleDbDataAdapter(cmd);
builder = new OleDbCommandBuilder(adapter);
ds = new DataSet("MainDataSet");
tempDs = new DataSet("TempDataSet");
connection.Open();
adapter.Fill(tempDs);
tempDs.Clear();
tempDs.Dispose();
adapter.Fill(ds, ddTables.Text);
userTable = ds.Tables[ddTables.Text];
}
catch
{
ClientScript.RegisterStartupScript(this.GetType(), "myalert", "alert('Could not load the data');", true);
}
finally
{
if (reader != null) reader.Close();
//if (connection != null) connection.Close();
datagrid.ShowFooter = true;
}
CreateTempTable(0, 10);
ClientScript.RegisterStartupScript(this.GetType(), "myalert", "alert('DONE');", true);
}
private void ReadRecords2()
{
// datagrid.DataSource = null;
OleDbDataReader reader = null;
try
{
connection = new OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0; " + "Data Source=" + databasePath);
OleDbCommand cmd = new OleDbCommand("Select * FROM " + ddTables.Text, connection);
adapter = new OleDbDataAdapter(cmd);
builder = new OleDbCommandBuilder(adapter);
ds = new DataSet("MainDataSet");
tempDs = new DataSet("TempDataSet");
connection.Open();
adapter.Fill(tempDs);
tempDs.Clear();
tempDs.Dispose();
adapter.Fill(ds, ddTables.Text);
userTable = ds.Tables[ddTables.Text];
}
catch
{
ClientScript.RegisterStartupScript(this.GetType(), "myalert", "alert('Could not load the data');", true);
}
finally
{
if (reader != null) reader.Close();
//if (connection != null) connection.Close();
}
CreateTempTable(0, 10);
ClientScript.RegisterStartupScript(this.GetType(), "myalert", "alert('DONE');", true);
}
private void CreateTempTable(int startRecord, int noOfRecords)
{
try
{
userTable.Rows.Clear();
adapter.Fill(ds, "");
userTable = ds.Tables[""];
}
catch (Exception ex)
{
ClientScript.RegisterStartupScript(this.GetType(), "myalert", "alert('Could not load the data in CreateTempTable');", true);
}
datagrid.DataSource = userTable.DefaultView;
datagrid.DataBind();
}
protected void datagrid_RowEditing(object sender, GridViewEditEventArgs e)
{
datagrid.EditIndex = e.NewEditIndex;
ReadRecords();
}
protected void datagrid_SelectedIndexChanged(object sender, EventArgs e)
{
}
protected void datagrid_RowUpdated(object sender, GridViewUpdatedEventArgs e)
{
adapter.Update(userTable);
}
protected void datagrid_RowUpdating(object sender, GridViewUpdateEventArgs e)
{
adapter.Update(userTable);
ReadRecords();
}
protected void datagrid_RowCancelingEdit(object sender, GridViewCancelEditEventArgs e)
{
datagrid.EditIndex = -1;
ReadRecords();
}
protected void datagrid_RowDeleting(object sender, GridViewDeleteEventArgs e)
{
int rowToDelete = e.RowIndex;
datagrid.DeleteRow(rowToDelete);
adapter.Update(userTable);
ReadRecords();
}
}
}
It can :
- get the .mdb file
- get the tables in the file and display it
- read the data out of the selected table and display it in the gridview
- add the edit delete buttons
Now when I click the edit button, it makes the selected row editable.
But when I click the update button I get "Object reference not set to an instance of an object."
The code worked in the Forms application..
Is there any way the adapter.Update(userTable); will be able to work the same it worked in the forms application?
Can anybody please help me see my problem. If I can only get it to save the changes back to the .mdb file I would be extremely glad.