asp.net pdf 417 reader

asp.net pdf 417 reader

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Figure 10-8. Automatic sorting by LastName The sort is according to the data type of the column. Numeric and date columns are ordered from smallest to largest. String columns are sorted alphanumerically without regard to case, assuming the underlying DataTable.CaseSensitive property is false (the default setting). Columns that contain binary data cannot be sorted.

When you set SortParameterName, the ObjectDataSource will always call the version of your method that accepts a sort expression. If the data isn t sorted (for example, when the grid is first constructed), the ObjectDataSource will simply pass an empty string as the sort expression.

Unfortunately, ASP.NET does not expose any mechanism to automatically verify or encrypt query string data. This facility could work in almost the same way as the view state protection. Without these features, query string data is easily subject to tampering. In 25, you ll take a closer look at the .NET cryptography classes and learn how you can use them to build a truly secure query string.

The ObjectDataSource provides two options: If your select method returns a DataSet or DataTable, the ObjectDataSource can use the same automatic sorting used with the SqlDataSource. If your select method returns a custom collection, you need to provide a selection method that accepts a sort expression and performs the sorting. Once again, this behavior gives you enough flexibility to build a solution, but it s not necessarily the ideal arrangement. For example, instead of building a GetEmployees() method that can perform sorting, it might make more sense to create a custom EmployeeDetails collection class with a Sort() method. Unfortunately, the ObjectDataSource won t support this pattern. To use the sort parameter, you need to create a select method that accepts a single string parameter. You must then set the ObjectDataSource.SortParameterName property to identify the name of that parameter, as shown here: <asp:ObjectDataSource ID="sourceEmployees" runat="server" TypeName="DatabaseComponent.EmployeeDB" SelectMethod="GetEmployees" SortParameterName="sortExpression" />

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 GetEmployees() method in a database component that performs the sorting in this way: Public Function GetEmployees(ByVal sortExpression As String) As EmployeeDetails() Dim con As New SqlConnection(connectionString) Dim cmd As New SqlCommand("GetAllEmployees", con) cmd.CommandType = CommandType.StoredProcedure Dim adapter As New SqlDataAdapter(cmd) Dim ds As DataSet = New DataSet() Try con.Open() adapter.Fill(ds, "Employees") Catch err As SqlException ' Replace the error with something less specific. ' You could also log the error now. Throw New ApplicationException("Data error.") Finally con.Close() End Try ' Apply sort. Dim view As DataView = ds.Tables(0).DefaultView view.Sort = sortExpression ' Create a collection for all the employee records. Dim employees As New ArrayList()

The ObjectDataSource provides the same type of support for updatable data binding as the SqlDataSource. The first step is to specify the UpdateMethod, which needs to be a public instance method in the same class: <asp:ObjectDataSource ID="sourceEmployees" runat="server" TypeName="DatabaseComponent.EmployeeDB" SelectMethod="GetEmployees" UpdateMethod="UpdateEmployee" /> The challenge is in making sure the UpdateMethod has the right signature. As with the SqlDataSource, updates, inserts, and deletes automatically receive a collection of parameters from the linked data control. These parameters have the same names as the corresponding class properties. To understand how this works, it helps to consider a basic example. Assume you create a grid that shows a list of EmployeeDetails objects. You also add a column with edit links. When the user commits an edit, the GridView fills the ObjectDataSource.UpdateParameters collection with one parameter for each property of the EmployeeDetails class, including EmployeeID, FirstName, LastName, and TitleOfCourtesy. Then, the ObjectDataSource searches for a method named UpdateEmployee() in the EmployeeDB class. This method must have the same parameters, with the same names. That means this method is a match: public void UpdateEmployee(int employeeID, string firstName, string lastName, string titleOfCourtesy) { ... }

When you set SortParameterName, the ObjectDataSource will always call the version of your method that accepts a sort expression. If the data isn t sorted (for example, when the grid is first constructed), the ObjectDataSource will simply pass an empty string as the sort expression.