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Figure 6-4: Required field validator control example 3

Figure 6-4 looks just like the example for "Classic ASP" in Figure 6-1, but underneath the covers, ASP.NET has written the validation code for you.

Now that you have looked at a quick example of using .NET validation, Table 6-1 gives you a more detailed description of the properties for the RequiredFieldValidator control.

The ControlToValidate and Display properties from Table 6-1 are explained in more detail in the following sections.

ControlToValidate property

Set this property's value to the name of the control to validate. If you refer to the code listing, this property was set to First to indicate that a value is required for this control.

Display property

You can set this property to one of three values to determine how the error message is displayed on the page if validation fails:

§Dynamic: The validator is displayed inline on the Web page if validation fails. The validator only takes up space on the page when the validator is visible. This allows multiple validators to occupy the same physical location on the Web page when those validators become visible. To avoid the Web page layout changing the validator becomes vi sible, the HTML element containing the validator must be large enough to accommodate the size of the validator.

§Static: The validator is displayed inline on the Web page if validation fails. Also, if the validator is hidden and becomes visible, the page layout does not change.

§None: The validation contents are not displayed inline on the Web page, the error message is displayed in the ValidationSummary control.

Using the CompareValidator Control

Use the CompareValidator control to make sure that a value matches a specified value. This control compares the value of an input control to another input control or a constant value using a variety of operators and types. You can also use this control to make sure that your input value is of a specific type: integer, string, and so on. Table 6-2 lists the commonly used properties for the CompareValidator control.

Table 6-2: Properties of the CompareValidator control

A good example for the CompareValidator control would be to compare passwords the first time a user creates an account in your Web application. The following code fragment shows the code for the CompareValidator control:

<!-- Compare Field Validator -->

Password:<br>

<asp:textbox id="Password" maxlength="16" runat="Server"/><br>

Confirm:<br>

<asp:textbox id="Confirm" maxlength="16" runat="Server"/>

<asp:comparevalidator

id="cvPasswords"

controltocompare="Password"

controltovalidate="Confirm"

display="dynamic"

errormessage="Passwords do not match, please try again."

runat="Server">

</asp:comparevalidator>

Launch your browser and navigate to Compare.aspx. Figure 6-5 should be displayed.

Now, enter the same values for the Password and Confirm fields and click the Validate button. Because the passwords match, the error message should not be displayed and you should see your message displayed on the page, as in Figure 6-7.

Figure 6-7: Compare validator control example 3

This is just one example of using the CompareValidator control. As shown earlier in Table 6-2, you could specify the ValueToCompare property instead of the ControlToCompare property. Try it! Delete the ControlToCompare property, add the ValueToCompare property, and set its value to some test value. Then run the Compare.aspx sample again. Validation will fail if the value entered in the

ControlToValidate field does not match the value in the ValueToCompare property.

Note This control is case-sensitive. For instance "RICK = Rick" will not compare as being equal.

Using the RangeValidator Control

Use the RangeValidator control to determine whether a value falls within the specified range. It checks whether the value of the associated input control is within some minimum and maximum, which can be a constant value or the value of another control. Table 6-3 lists the properties commonly used with the RangeValidator control.

Type property

You can set the Type property to one of the following values, which determines the type of values in the range:

§*Currency: The data type is Currency.

§*Date: The data type is DateTime.

§*Double: The data type is Double.

§*Integer: The data type is Integer.

§*String: The data type is String.

MinimumValue and MaximumValue properties

The RangeValidator control is useful when you need to make sure that a value falls within a specified range of values. Take a look at the code fragment that follows for the RangeValidator control:

<!-- Range Validator Control -->

Number of tickets:<br>

<asp:textbox id="Tickets" maxlength="2" columns="2" runat="Server"/>

<asp:rangevalidator