ADO.NET Part 2

Slide 2 Overview

Slide 3 Introduction to the DataGridView Control It’s a two-dimensional grid containing rows and columns Its use in unbound mode was mentioned earlier in the course Now, we will use it in bound mode

Slide 4 The DataGridView Control (Capabilities) Displays rows from a single table ( DataTable ) or view Allows editing (add, change, delete) A rich set of events for error handling A rich set of properties and objects for formatting

Slide 5 The DataGridView Control (Binding) Set the DataSource and DataMember properties These can be A DataSet ( DataSource ) and DataTable ( DataMember ) A BindingSource ( DataSource – the DataMember is not set)

Slide 6 The DataGridView Control (Formatting) Much can be done through the user interface

Slide 7 The DataGridView Control (Columns Editor)

Slide 8 DataGridView (Row Events) In all, there are about 100 different events Only selected events are of interest to us RowEnter fires as a row gets input focus RowLeave fires as a row loses focus RowValidating fires after RowLeave and provides the chance for validation This event can be cancelled

Slide 9 DataGridView (Row Events 2) Event arguments are complex types DataGridViewCellEventArgs RowIndex contains the 0-based index of the row ColIndex contains the 0-based index of the column DataGridViewCellCancelEventArgs Set Cancel to true to cancel the subsequent events

Slide 10 DataGridView (Row Events 3) See tblLocationDataGridView event handlers in IS389ADOPart 2

Slide 11 DataGridView (Cell Events 1) CellEnter fires when a cell gets focus CellBeginEdit fires when editing begins CellEndEdit fires when editing ends CellLeave fires after end edit when cell loses focus

Slide 12 DataError Event Remember that in this context, the DataGridView is bound to a data source Trying to store type invalid values in the underlying DataTables will throw exceptions Handle this event to handle those exceptions

Slide 13 Using the OleDbCommand Object ( ExecuteScalar ) Remember the ExecuteScalar method returns a single value Use to get a max ID value

Slide 14 ExecuteScalar (Example) Get Max of field fldBoreHoleID in tblBoreHoleData System.Data.OleDb.OleDbCommand oCmd = new System.Data.OleDb.OleDbCommand(); oCmd.CommandType = CommandType.Text; oCmd.CommandText = "SELECT MAX(fldBoreHoleID) FROM tblBoreholeData"; oCmd.Connection = tblBoreholeDataTableAdapter.Connection; oCmd.Connection.Open(); int i; i = (int) oCmd.ExecuteScalar(); oCmd.Connection.Close();

Slide 15 Using the OleDbCommand Object ( ExecuteNonQuery ) Use to Execute INSERT, UPDATE, or DELETE commands that do not return rows Example 1: System.Data.OleDb.OleDbCommand oCmd = new System.Data.OleDb.OleDbCommand(); oCmd.CommandType = CommandType.Text; oCmd.CommandText = "INSERT INTO tblCasIndex (fldCASIndexNumber, fldChemicalName, fldCASRegNo, fldCarcinogenic) VALUES (123,'abc','def',false)"; oCmd.Connection = tblBoreholeDataTableAdapter.Connection; oCmd.Connection.Open(); oCmd.ExecuteNonQuery(); oCmd.Connection.Close();

Slide 16 Using the OleDbCommand Object with Parameters Unlike the previous example, we generally don’t want to hardcode the data values This is where parameters come in Add one parameter for each dynamic field

Slide 17 Creating a Parameter An OleDbParameter has a Name Data type Size Mapping field Example: System.Data.OleDb.OleDbParameter prop = new System.Data.OleDb.OleDbParameter( "fldCASIndexNumber",System.Data.OleDb.O leDbType.Integer,0,"fldCASIndexNumber") ;

Slide 18 Adding the Parameter Each parameter must be added to the Parameters collection of the OleDbCommand Example oCmd.Parameters.Add(prop);

Slide 19 Filling in the Parameter Values Set the Value property of a particular parameter oCmd.Parameters["fldCASIndexNumber"].Value = 234; oCmd.Parameters["fldChemicalName"].Value = "XXX"; oCmd.Parameters["fldCASRegNo"].Value = "YYY"; oCmd.Parameters["fldCarcinogenic"].Value = true;

Slide 20 A Parameterized insert statement The INSERT statement looks like this oCmd.CommandText = "INSERT INTO tblCasIndex (fldCASIndexNumber, fldChemicalName, fldCASRegNo, fldCarcinogenic) VALUES (?,?,?,?)";

Slide 21 Using the OleDbDataReader Place an SQL SELECT statement in the OleDbcommand Call ExecuteReader to create the forward- only reader Call Read to read each record Then call the various Get method to get the value of each field

Slide 22 Programmatically Selecting Records See Example