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Now you have to implement the GetEmployees() method and decide how you want to perform the sorting. The easiest approach is to fill a disconnected DataSet so you can rely on the sorting functionality of the DataView. Here s an example of a GetEmployess() method in a database component that performs the sorting in this way: public EmployeeDetails[] GetEmployees(string sortExpression) { SqlConnection con = new SqlConnection(connectionString); SqlCommand cmd = new SqlCommand("GetAllEmployees", con); cmd.CommandType = CommandType.StoredProcedure; SqlDataAdapter adapter = new SqlDataAdapter(cmd); DataSet ds = new DataSet(); try { con.Open(); adapter.Fill(ds, "Employees"); } catch (SqlException err) { // Replace the error with something less specific. // You could also log the error now. throw new ApplicationException("Data error."); } finally { con.Close(); } // Apply sort. DataView view = ds.Tables[0].DefaultView; view.Sort = sortExpression; // Create a collection for all the employee records. ArrayList employees = new ArrayList(); foreach (DataRowView row in view) { EmployeeDetails emp = new EmployeeDetails( (int)row["EmployeeID"], (string)row["FirstName"], (string)row["LastName"], (string)row["TitleOfCourtesy"]); employees.Add(emp); } return (EmployeeDetails[])employees.ToArray(typeof(EmployeeDetails)); } Another approach is to change the actual query you re executing in response to the sort expression. This way, your database can perform the sorting. This approach is a little more complicated, and no perfect option exists. Here are the two most common possibilities: You could dynamically construct a SQL statement with an ORDER BY clause. However, this risks SQL injection attacks, unless you validate your input carefully. You could write conditional logic to examine the sort expression and execute different queries accordingly (either in your select method or in the stored procedure). This code is likely to be fragile and involves a fair bit of string parsing.

Remember, if you set the DataKeyNames property of the rich data control, the names of key fields will be changed (based on the ObjectDataSource.OldValuesParameterFormatString property). See the section Updating and Key Fields earlier in this chapter for more information.

GridView1.DataKeys(row.RowIndex).Value.ToString() If keyValue = selectedValue Then GridView1.SelectedIndex = row.RowIndex Return End If Next End If End Sub Keep in mind that this approach can be confusing if you also have enabled paging (which is described later in the section Paging the GridView ). That s because a sorting operation might move the current row to another page, rendering it not visible but keeping it selected. This is a perfectly valid situation from a code standpoint but confusing in practice.

If you use sorting and selection at the same time, you ll discover another issue To see this problem in action, select a row, and then sort the data by any column You ll see that the selection will remain, but it will shift to a new item that has the same index as the previous item In other words, if you select the second row and perform a sort, the second row will still be selected in the new page, even though this isn t the record you selected The only way to solve this problem is to programmatically change the selection every time a header link is clicked The simplest option is to react to the GridViewSorted event to clear the selection, as shown here: protected void GridView1_Sorted(object sender, GridViewSortEventArgs e) { // Clear selected index GridView1.

One problem with the UpdateEmployee() method shown in the previous example is that the method signature is a little cumbersome you need one parameter for each property in the data object. Seeing as you already have a definition for the EmployeeDetails class, it makes sense to create an UpdateEmployee() method that uses it and gets all its information from an EmployeeDetails object. Here s an example: public void UpdateEmployee(EmployeeID emp) { ... } The ObjectDataSource supports this approach. However, to use it, you must set the DataObjectTypeName to the full name of the class you want to use. Here s how it works: <asp:ObjectDataSource ID="sourceEmployees" runat="server" TypeName="DatabaseComponent.EmployeeDB" DataObjectTypeName="DatabaseComponent.EmployeeDetails" ... /> Once this is in place, the ObjectDataSource will match only the UpdateMethod, DeleteMethod, or InsertMethod if it has a single parameter that accepts the type specified in DataObjectTypeName. Additionally, your data object must follow some rules: It must provide a default (zero-argument) constructor. For every parameter, there must be a property with the same name. (Public variables are ignored.) All properties must be public and writable. You re free to add code to your data object class. For example, you can add methods, constructors, validation and event-handling logic in your property procedures, and so on.

The GridView s sorting is straightforward it supports sorting by any sortable column in ascending order In some applications, the user has more sorting options or can order lengthy result sets with more complex sorting expressions Your first avenue for improving sorting with the GridView is to handle the GridViewSorting event, which occurs just before the sort is applied At this point, you can change the sorting expression For example, you could use this to implement an ascending/descending sort pattern With this pattern, you click a column once to apply an ascending sort and a second time to apply a descending sort This is similar to the sorting that s built into Windows Explorer Here s the code you need to implement this approach: Protected Sub GridView1_Sorting( ByVal sender As Object, ByVal e As GridViewSortEventArgs) ' Check to see the if the current sort (GridView1.