PART III in C#

Encode UCC - 12 in C# PART III

Table 12-3

After the project is created, open up WebForm1 in HTML view and add the following ASPNET lines to the form:

<form id="Form1" method="post" runat="server"> <asp:Label ID="lblFName" Runat="server">First Name</asp:Label> <asp:TextBox ID="txtFName" Runat="server" Width="170px" /> <asp:RequiredFieldValidator ID="valFName" Runat="server" ErrorMessage="You must enter a First Name" ControlToValidate="txtFName" Display="Dynamic" /> <br> <br> <asp:Button ID="btnSend" Runat="server" Text="Click Me!" /> <br> <br> <asp:Label ID="lblDisplay" Runat="server" /> </form>

Then add a click event handler for the button (double-click the button in Design View) as follows:

private void btnSend_Click(object sender, SystemEventArgs e) { lblDisplayText=txtFNameText; }

When you run the application and click the Click Me button without entering a first name in the TextBox control, the display looks like this:

The RequiredFieldValidator uses a number of attributes to control its behavior The more important ones are the ErrorMessage, which specifies the message to be displayed when the validation fails; ControlToValidate, which specifies the control to bind the validator to; and Display, which specifies the behavior of the validator (None means it is hidden, Dynamic sets it to be visible when needed, and Static makes it visible all the time) If you set the Display attribute to None, the validator will not display any messages This setting is normally used when the form has a ValidationSummary control that will display the messages from all the validators on the page at one time By changing the code in the form to match the following code, you can take advantage of the ValidationSummary control

<form id="Form1" method="post" runat="server"> <asp:Label ID="lblFName" Runat="server">First Name</asp:Label> <asp:TextBox ID="txtFName" Runat="server" Width="170px" /> <asp:RequiredFieldValidator ID="valFName" Runat="server" ErrorMessage="You must enter a First Name" ControlToValidate="txtFName" Display="None" /> <br> <br> <asp:Button ID="btnSend" Runat="server" Text="Click Me!" /> <br> <br> <asp:Label ID="lblDisplay" Runat="server" /> <br />

<asp:ValidationSummary ID="validationSummary" Runat="server" HeaderText="Before you submit your request:"/> </form>

Now you can start adding some of the other validator controls to see how they operate Let s add a CompareValidator as well as a RangeValidator to our form, along with two TextBox controls one for age, and the other for salary The range for the accepted age will be from 1 to 125 years, and the salary must be positive The following code will create that form:

<form id="Form1" method="post" runat="server"> <asp:Label ID="lblFName" Runat="server">First Name</asp:Label> <asp:TextBox ID="txtFName" Runat="server" Width="170px" /> <asp:RequiredFieldValidator ID="valFName" Runat="server" ErrorMessage="You must enter a First Name" ControlToValidate="txtFName" Display="None" /> <br> <asp:Label ID="lblAge" Runat="server">Age</asp:Label> <asp:TextBox ID="txtAge" Runat="server" Width="80px"/> <asp:RangeValidator ID="rangeValidator" Runat="server"

ErrorMessage="Your age must be from 1 to 125 years" ControlToValidate="txtAge" MinimumValue="1" MaximumValue="125" Display="None"/> <br> <asp:Label ID="lblSalary" Runat="server">Salary</asp:Label> <asp:TextBox ID="txtSalary" Runat="server" Width="120px" /> <asp:CompareValidator ID="compareValidator" Runat="server" ErrorMessage="Your salary must be positive" ControlToValidate="txtSalary" Operator="GreaterThan" ValueToCompare="0" Display="None"/> <br> <asp:Button ID="btnSend" Runat="server" Text="Click Me!" /> <br> <br> <asp:Label ID="lblDisplay" Runat="server" /> <br> <asp:ValidationSummary ID="validationSummary" Runat="server" HeaderText="Before you submit your request:"/> </form>

Make use of the validation controls to ensure the data collected from the client is within the right ranges and that fields that should have entries do indeed have them The RegularExpressionValidator uses the regular expressions that UNIX and Perl developers are used to; these expressions are very powerful string-manipulation statements and are beyond the scope of the book The CustomValidator control uses a client-side script to validate the content of the control Unfortunately, you cannot use C# on the client s browser EXAM TIP The CustomValidator control uses client-side script languages such as VBScript or JScript to validate the control

The reality of the web developer s world is that there is always a need for more powerful controls than those supplied with the environment To solve that problem, you have user controls and custom controls User controls allow the developer to take an existing ASPNET page and turn it into a control, very much like the scriptlets in ASP 30 Custom controls are a control type that mimic the ActiveX controls of previous versions of Visual Studio custom controls allow you to combine many controls into one logical control that is then used in the web application The creation and use of user and custom controls are detailed in 14