asp.net ean 13

vb.net ean-13 barcode

creating barcode vb.net, vb.net code 128 barcode, asp.net code 39 barcode, datamatrix net examples, ean 128 .net, .net ean 13, .net pdf 417, qrcode.net example, upc nejde internet

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.

Repeated-value binding allows you to bind an entire list of information to a control. This list of information is represented by a data object that wraps a collection of items. This could be a collection of custom objects (for example, with an ordinary ArrayList or Hashtable) or a collection of rows (for example, with a DataReader or DataSet). ASP.NET includes several basic list controls that support repeated-value binding: All controls that render themselves using the <select> tag, including the HtmlSelect, ListBox, and DropDownList controls The CheckBoxList and RadioButtonList controls, which render each child item with a separate check box or radio button The BulletedList control, which creates a list of bulleted or numbered points All these controls display a single-value field of a property from each data item. When dealing with one of these controls, you ll find the properties listed in Table 9-1. Table 9-1. Data Properties for List Controls

For example, if you add a breakpoint to the code in a web page (as discussed in the Visual Studio Debugging section later in this chapter), Visual Studio stores the breakpoint in the suo file so it s still there when you open the project later Similarly, Visual Studio tracks the currently open files so it can restore your view when you return to the project This approach to solution management is fragile obviously, if you move the project from one location to another, you lose all this information However, because this information isn t really all that important (think of it as a few project-specific preferences), losing it isn t a serious problem The overall benefits of a projectless system are worth the trade-off..

Sometimes you may run into a problem in which the property names of your data class don t exactly match the parameter names of your update method. If all you need is a simple renaming job, you need to perform the task that was described in the Updating with Stored Procedures section earlier, although the syntax is slightly different. First, you define the additional parameters you need, with the correct names. For example, maybe you need to rename the EmployeeDetails.EmployeeID property to a parameter named id in the update method. Here s the new parameter you need: <asp:ObjectDataSource ID="sourceEmployees" runat="server" TypeName="DatabaseComponent.EmployeeDB" SelectMethod="GetEmployees" UpdateMethod="UpdateEmployee" OnUpdating="sourceEmployees_Updating" > <UpdateParameters> <asp:Parameter Name="id" Type="Int32" /> </UpdateParameters> </asp:ObjectDataSource> Second, you react to the ObjectDataSource.Updating event, setting the value for these parameters and removing the ones you don t want: protected void sourceEmployees_Updating(object sender, ObjectDataSourceMethodEventArgs e) { e.InputParameters["id"] = e.InputParameters["EmployeeID"]; e.InputParameters.Remove("EmployeeID"); }

This is a data object that contains the data to display. This data object must implement a supported interface, typically ICollection. Instead of supplying the data object programmatically (using code), you can link your list control to a data source control by setting this property. The data source control will generate the required data object automatically. You can use either the DataSource property or the DataSourceID property, but not both. Every data source represents a collection of data items. A list control can display only a single value from each list item. The DataTextField indicates the field (in the case of a row) or property (in the case of an object) of the data item that contains the value to display in the page. Specifies an optional format string that the control will use to format each DataTextValue before displaying it. This property is similar to the DataTextField property, but the value from the data item isn t displayed in the page instead, it s stored in the value attribute of the underlying HTML tag. This allows you to retrieve the value later in your code. The primary use of this field is to store a unique ID or primary key field so you can use it later to retrieve more data when the user selects a specific item.