通过datagridview实时更新MDB数据库

Question

I am currently trying to create a small program that takes the data from a MDB database that is displayed in a datagridview. The program should allow the user to modify (add, update, delete) the data in the datagridview. Furthermore everything should be updated to the MDB automatically (no buttons). I know there are a lot of topics out there regarding this subject, however for some reason I am unable to reproduce the same results.

I am able to retrieve the data from the MDB file and display it in the datagridview but I am unable to add, modify or delete data. The program keeps throwing exceptions at me but I don't understand why.

First the user has to create a database. The database is generated automatically by code.

private void CreateNewDatabase_Click(object sender, EventArgs e)
{
    string DB_FILENAME = "c:\Test.mdb";

    // GENERATE THE ACCESS FILES, ITS TABLES AND ITS COLUMNS

    var cnnStr = "Provider=Microsoft.Jet.OLEDB.4.0.;Data Source=" + DB_FILENAME; //Use a late bound COM object to create a new catalog. This is so we avoid an interop assembly
    var catType = Type.GetTypeFromProgID("ADOX.Catalog");
    object o = Activator.CreateInstance(catType);
    catType.InvokeMember("Create", System.Reflection.BindingFlags.InvokeMethod, null, o, new object[] { cnnStr });
    OleDbConnection cnn = new OleDbConnection(cnnStr);
    cnn.Open();
    var cmd = cnn.CreateCommand();

    // CREATE SCHEDULE TABLE
    cmd.CommandText = "CREATE TABLE SCHEDULE ([ID] IDENTITY PRIMARY KEY, [Day] TEXT, [Month] TEXT, [Year] TEXT, [IMS] TEXT, [Customer] TEXT, [Short Description] TEXT, [Long Description] TEXT, [Delivery Ticket Number] TEXT, [Returned] TEXT)";
    cmd.ExecuteNonQuery();

    cmd.CommandText = "INSERT INTO SCHEDULE ([ID]) VALUES (1)";
    cmd.ExecuteNonQuery();

    // DISPOSE OF THE VARIABLES USED
    cnn.Close();
    cnn.Dispose();
    cmd.Dispose();

}

Once the database has been created it is used in a windows form with a datagridview in it.

public void Initialize()
{

    Con = new OleDbConnection(@"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + sttngs.DBloc);
    Con.Open();

    // TRY TO OPEN THE DATABASE FILE AND POPULATE THE DATAGRIDVIEW
    da = new OleDbDataAdapter("SELECT [Day], [Month], [Year], [IMS], [Customer], [Short Description], [Long Description], [Delivery Ticket Number], [Returned] FROM SCHEDULE",Con); // WHERE [Returned] = '" + "NO' ", Con);

    // POPULATE cBuilder
    cBuilder = new OleDbCommandBuilder(da);
    ScheduleData = new DataTable();
    da.Fill(ScheduleData);

    if (ScheduleData.Rows.Count > 0)
    {
       BindingSource BDS = new BindingSource();
       BDS.DataSource = ScheduleData;
       this.dataGridView.DataSource = BDS;        
    }
}

Once the data in the datagridview is changed (handled by the CellValidating event) the data should be updated in the MDB.

 private void dataGridView_CellValidating(object sender, DataGridViewCellValidatingEventArgs e)
 {
     if (ScheduleData.GetChanges() != null)
     {
        dataGridView.EndEdit();
        da.Update(ScheduleData);
        ScheduleData.AcceptChanges();
     }
 }

The code is pretty straight forward but for some reason I am unable to figure out why the data in the MDB is not updated. I have been stuck for a while now so any help would be great!

Answer 1

One thing I can see that will cause an issue is that when you setup your commandbuilder you are not requesting the relevant UPDATE, DELETE & INSERT commands.

When you generate the command builder like this :-

cBuilder = new OleDbCommandBuilder(da);

Follow up with :-

cBuilder.GetUpdateCommand();
cBuilder.GetInsertCommand();
cBuilder.GetDeleteCommand();

You may need to declare all of this in Cell Validating, I'm unsure. Give It a try.

Look this MSDN article over, its for the SQLcommamdbuilder, but the same rules apply :-

http://msdn.microsoft.com/en-us/library/system.data.sqlclient.sqlcommandbuilder.aspx

Also, You have no open connection to the Data Adapter as you try to update it :-

if (ScheduleData.GetChanges() != null)
     {
        dataGridView.EndEdit();

        //Open a connection Here
        da.Update(ScheduleData);

        ScheduleData.AcceptChanges();
     }

Your SQL String is incorrect, try :-

"SELECT (Day, Month, Year, IMS, Customer, Short Description, Long Description, Delivery Ticket Number, Returned) FROM [SCHEDULE]"