Update Query始终更新为-1 - C＃，Microsoft访问

Question

问题是例如当我尝试更新姓氏时，它总是更新-1。 Ms-Access是数据库。

private void btnUpdate_Click(object sender, EventArgs e)
{
    belobj.UserID = Convert.ToInt32(txtCustomerId.Text);
    belobj.Firstname = txtFirstName.Text;
    belobj.Lastname = txtLastName.Text;
    belobj.Email = txtEmail.Text;
    belobj.Username = txtUserName.Text;
    belobj.Password = txtPassword.Text.Trim();
    belobj.Enable = cmbEnable.Text.Trim();
    if (gridcheck == true)
    {
        DialogResult dialogResult = MessageBox.Show("Do you want to save all pending changes ?", "Save Changes", MessageBoxButtons.YesNo);
        if (dialogResult == DialogResult.Yes)
        {
               string query = string.Format("UPDATE tbl_User SET Firstname= '" + belobj.Firstname + "' and  Lastname= '" + belobj.Lastname + "' and Email= '" + belobj.Email + "' and Username= '" + belobj.Username + "' and Password= '" + belobj.Password + "' and Enable='" + belobj.Enable + "' where [UserID]= " + belobj.UserID + "");

            if (balobj.UpdateQuery(query, belobj) > 0)
            {
                MessageBox.Show("Record Upadted Succesfully");
                GenerateCustomerId();
            }
            else
            {
            }
            gridcheck = false;
        }
        else if (dialogResult == DialogResult.No)
        {
            gridcheck = false;
            BindGrid();
            ControlClear();
            GenerateCustomerId();
        }
    }
    else
    {
        MessageBox.Show("Please select Any Customer !!");
        return;
    }
}  

public int ExecuteUpdateQuery(String _query, BEL belobj)
{
    try
    {
        oledbcomm.Connection = openConnection();
        oledbcomm.CommandText = _query;


        oledbcomm.Parameters.Add(new OleDbParameter("Firstname", belobj.Firstname));
        oledbcomm.Parameters.Add(new OleDbParameter("Lastname", belobj.Lastname));
        oledbcomm.Parameters.Add(new OleDbParameter("Email", belobj.Email));
        oledbcomm.Parameters.Add(new OleDbParameter("Username", belobj.Username));
        oledbcomm.Parameters.Add(new OleDbParameter("Password", belobj.Password));
        oledbcomm.Parameters.Add(new OleDbParameter("Enable", belobj.Enable));
        oledbcomm.Parameters.Add(new OleDbParameter("UserID", Convert.ToInt32(belobj.UserID)));

        int x = oledbcomm.ExecuteNonQuery();

        return x;
    }
    catch (Exception ex)
    {
        throw ex;
    }
    finally
    {
        oledbcomm.Dispose();
        con.Close();
    }
}