c# - Error : Update requires a valid UpdateCommand when passed DataRow collection with modified rows

Question

I am using Paging to show data in datagridview, but when i try to Update any data with updatebutton data should be updated In datagridview as well as in database.

But I get this error:

Update requires a valid UpdateCommand when passed DataRow collection with modified rows

which happens on this line:

adp1.Update(dt);//here I am getting error

Below is the code

public partial class EditMediClgList : Form
    {        
        public EditMediClgList()
        {
            InitializeComponent();
            try
            {
                con = new OleDbConnection(@"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=db1.mdb");
                con.Open();
            }
            catch (Exception err)
            {
                MessageBox.Show("Error:" +err);
            }

            cmd1 = new OleDbCommand("Select * from MedicalColeges order by MedicalClgID", con);
            ds = new DataSet();
            adp1 = new OleDbDataAdapter(cmd1);
            adp1.Fill(ds, "MedicalColeges");
            dataGridView1.DataSource = ds;

            // Get total count of the pages; 
            this.CalculateTotalPages();
            // Load the first page of data; 
            this.dataGridView1.DataSource = GetCurrentRecords(1, con);

        }
        private void CalculateTotalPages()
        {
            int rowCount = ds.Tables["MedicalColeges"].Rows.Count;
            this.TotalPage = rowCount / PageSize;
            if (rowCount % PageSize > 0) // if remainder is more than  zero 
            {
                this.TotalPage += 1;
            }
        }
        private DataTable GetCurrentRecords(int page, OleDbConnection con)
        {
             dt = new DataTable();

            if (page == 1)
            {
                cmd2 = new OleDbCommand("Select TOP " + PageSize + " * from MedicalColeges ORDER BY MedicalClgID", con);
                // CurrentPageIndex++;
            }
            else
            {
                int PreviouspageLimit = (page - 1) * PageSize;

                cmd2 = new OleDbCommand("Select TOP " + PageSize +
                    " * from MedicalColeges " +
                    "WHERE MedicalClgID NOT IN " +
                "(Select TOP " + PreviouspageLimit + " MedicalClgID from MedicalColeges ORDER BY MedicalClgID) ", con); // +
                //"order by customerid", con);
            }
            try
            {
                // con.Open();
                this.adp1.SelectCommand = cmd2;
                this.adp1.Fill(dt);
                txtPaging.Text = string.Format("page{0} of {1} pages", this.CurrentPageIndex, this.TotalPage);
            }
            finally
            {
               // con.Close();
            }
            return dt;
        }

        private void button1_Click(object sender, EventArgs e)
        {
            try
            {                
                adp1.Update(dt);//here I am getting error
            }
            catch (Exception err)
            {
                MessageBox.Show(err.Message.ToString());
            }

        }
}

Answer 1

You have Created the OleDbDataAdapter with a Select command only:

adp1 = new OleDbDataAdapter(cmd1);

OleDbDataAdapter requires valid Update, Insert, Delete commands to be used to save the data like this:

adp1.Update(dt);//here I am getting error

You just need to use a OleDbCommandBuilder that will generate the commands for you:

adp1 = new OleDbDataAdapter();
adp1.SelectCommand = cmd1; // cmd1 is your SELECT command
OleDbCommandBuilder cb = new OleDbCommandBuilder(adp1);

EDIT

Since you change the Select command of the OleDbDataAdapter at runtime for paging, what your need is to initialize each time you save data:

private void button1_Click(object sender, EventArgs e)
    {
        try
        {                
            adp1.SelectCommand = cmd1; // cmd1 is your SELECT command
            OleDbCommandBuilder cb = new OleDbCommandBuilder(adp1);
            adp1.Update(dt); //here I hope you won't get error :-)
        }
        catch (Exception err)
        {
            MessageBox.Show(err.Message.ToString());
        }

    }