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Walkthrough: Creating and Using an ASP.NET Web Service in Visual Web Developer

  • Článek

Note

This topic pertains to a legacy technology. XML Web services and XML Web service clients should now be created using Windows Communication Foundation.

In addition to letting you create Web pages, Microsoft Visual Studio also lets you create Web services that use ASP.NET XML. Creating a Web service in Visual Studio is similar to creating a Web page. You can also use the Microsoft Visual Web Developer Web development tool to reference and use Web services that are in a Visual Web Developer solution, on your local computer or in a local or external UDDI directory. In this walkthrough, you will create the Web service in one solution and use it in another.

Tasks illustrated in this walkthrough include:

  • Creating a simple XML Web service in Visual Web Developer.

  • Creating a separate Web site that uses the Web service.

Prerequisites

In order to complete this walkthrough, you will need:

  • Microsoft Internet Information Services (IIS) installed locally on your computer.

  • .NET Framework version 3.5 or higher.

Creating a Web Service Under the IIS Root

Create a new Web service and page by following these steps.

Note

You must use an IIS Web site for this walkthrough.

To create a Web service

  1. Open Visual Web Developer.

  2. On the File menu, click New Web Site.

    The New Web Site dialog box appears.

  3. Under Visual Studio installed templates, click ASP.NET Web Service.

  4. Click Browse.

  5. Click Local IIS.

  6. Click Default Web Site.

  7. Click Create New Web Application.

    Visual Web Developer creates a new IIS Web application.

  8. Type the name TemperatureWebService.

  9. Click Open.

    The New Web Site dialog box appears, with the name of the new Web site in the rightmost Location list. The location includes the protocol (http://) and location (localhost). This indicates that you are working with a local IIS Web site.

  10. In the Language list, click the programming language that you prefer to work in.

    The programming language that you choose will be the default for the Web site. However, you can use more than one language in the same Web application by creating pages and components in different programming languages. For more information about how to create components using different languages, see Shared Code Folders in ASP.NET Web Site Projects.

  11. Click OK.

    Visual Web Developer creates the new Web service and opens a new class named Service, which is the default Web service. However, in the following procedure you will create a new Web service with a specified name and you will not use the Service class.

  12. Close the Service class.

Creating the Web Service

You will create a Web service that converts temperature from Fahrenheit to Celsius and vice versa.

To create the Web service

  1. In Solution Explorer, right-click the Web site name (https://localhost/TemperatureWebService), and then click Add New Item.

  2. Under Visual Studio installed templates, click Web Service, and then in the Name box, type Convert.

  3. Make sure that the Place code in separate file check box is selected, and then click Add.

    Visual Web Developer creates a new Web service that is made up of two files. The Convert.asmx file is the file that can be invoked to call Web service methods, and it points to the code for the Web service. The code itself is in a class file (Convert.vb, Convert.cs, or Convert.jsl, depending on the programming language) in the App_Code folder. The code file contains a template for a Web service. The code file includes some code for a Web service method.

You will create two methods in the Web service. The first method converts Fahrenheit temperatures to Celsius, and the second method converts Celsius temperatures to Fahrenheit.

To create the conversion methods

  1. Add the following code inside the class, after the HelloWorld method:

        <System.Web.Services.WebMethod()> _
Public Function FahrenheitToCelsius(ByVal Fahrenheit As Double) _
        As Double
        Return ((Fahrenheit - 32) * 5) / 9
    End Function

    <System.Web.Services.WebMethod()> _
        Public Function CelsiusToFahrenheit(ByVal Celsius As Double) _
            As Double
        Return ((Celsius * 9) / 5) + 32
    End Function

    [System.Web.Services.WebMethod()]
public double FahrenheitToCelsius(double Fahrenheit)
{
    return ((Fahrenheit - 32) * 5) / 9;
}

[System.Web.Services.WebMethod()]
public double CelsiusToFahrenheit(double Celsius)
{
    return ((Celsius * 9) / 5) + 32;
}

    Notice that the function names are preceded with an attribute ([System.Web.Services.WebMethod()] or <System.Web.Services.WebMethod()>) as part of the function declaration.

  2. After you have entered the functions, save the file.

Now, you can test the Web service in Visual Web Developer.

To test the Web service

  1. In Solution Explorer, click Convert.asmx, and then press CTRL+F5.

    The Web service is invoked and a page appears in the browser that shows the methods that are exposed by the Web service.

  2. Click CelsiusToFahrenheit, which invokes that method.

    A page appears that prompts you for parameter values for the CelsiusToFahrenheit method.

  3. In the Celsius box, type 100, and then click Invoke.

    A new window appears that displays the XML that the Web service returns when the CelsiusToFahrenheit method is invoked. The value 212 appears in the XML.

  4. Close the browser that contains the method results.

  5. In the original browser, click Back to return to the list of methods.

  6. Click FahrenheitToCelsius and test to make sure that the method is returning the results that you expect.

    If you type 212, the FahrenheitToCelsius method will return 100.

  7. Close the browser.

You have finished creating the Web service; the next step is to use it.

Using the Web Service

Now that you have a Web service, you will create a Web site where you will reference and use the Web service that you created. For the walkthrough, you will create a separate Web site that has a page where you start the Web service methods that you just created.

To create a Web site to use the Web service

  1. On the File menu, click New Web Site.

  2. Under Visual Studio installed templates, click ASP.NET Web Site.

  3. Click Browse.

  4. Click Local IIS.

  5. Click Default Web Site.

  6. Click Create New Web Application.

    Visual Web Developer creates a new IIS Web application.

  7. Type the name TemperatureWeb.

  8. Click Open.

  9. In the Language list, click the programming language that you prefer to work in.

  10. Click OK.

    Visual Web Developer creates a new local IIS Web site and a new page named Default.aspx.

Adding the Web Service as a Component

The Web service is a component that you can reference in your application. Therefore, you must create a reference to it.

To create a reference to the Web service

  1. On the Web Site menu, click Add Web Reference.

    The Add Web Reference dialog box appears, as shown in the following screen shot.

    Add Web Reference dialog box

    Add Web Reference dialog box

  2. In the URL list, enter the following URL for the Web service, and then click Go:

    https://localhost/TemperatureWebService/Convert.asmx

    When Visual Web Developer finds the Web service, information about the Web service appears in the Add Web References dialog box.

    Note

    If you cannot add a reference to a Web service, it might be that the proxy server is not configured correctly. In Microsoft Internet Explorer, on the Tools menu, click Internet Options, click Connections, and then click LAN Settings. Select the Bypass proxy server for local addresses check box. Additionally, set the proxy server address to the exact name of the proxy server instead of allowing Internet Explorer to detect the proxy server. For more information, contact the network administrator.

  3. Click one of the method links.

    The test page for the method appears.

  4. Click Add Reference.

    Visual Web Developer creates an App_WebReferences folder and adds a folder to it for the new Web reference. By default, Web references are assigned a namespace corresponding to their server name (in this case, localhost). Make a note of the name for the Web reference namespace. In the folder, Visual Web Developer adds a .wsdl file that references the Web service. It also adds supporting files, such as discovery (.disco and .discomap) files, that include information about where the Web service is located.

Note

If the server name for the Web service contains characters that cannot be used for a class name, such as a hyphen (-), Visual Web Developer converts those characters to an underscore character (_). Therefore, the namespace in Visual Web Developer for the Web service might not match the server name exactly.

You can now use the Web service. In this walkthrough, you will add controls to Default.aspx, and then program the controls to convert a specified temperature to both Fahrenheit and Celsius. When the page is running, it will look something like the following illustration.

Temperature conversion page

VenusWebServicesWalkthroughConsumePage screenshot

To call the Web service methods

  1. Open the Default.aspx page and switch to Design view.

  2. From the Standard group in the Toolbox, drag the following controls onto the page and set their properties as indicated:

    Control

    Properties

    Textbox

    ID: TemperatureTextbox

    Text: (empty)

    Button

    ID: ConvertButton

    Text: Convert

    Label

    ID: FahrenheitLabel

    Text: (empty)

    Label

    ID: CelsiusLabel

    Text: (empty)

  3. Optionally, add text to the page for captions.

    For this walkthrough, the layout of the page is not important.

  4. Double-click ConvertButton to create an event handler for its Click event.

  5. Make sure your event handler code matches the code in the following example.

    Dim wsConvert As New localhost.Convert()
Dim temperature As Double
temperature = System.Convert.ToDouble(TemperatureTextbox.Text)
FahrenheitLabel.Text = "Fahrenheit To Celsius = " & _
    wsConvert.FahrenheitToCelsius(temperature).ToString()
CelsiusLabel.Text = "Celsius To Fahrenheit = " & _
    wsConvert.CelsiusToFahrenheit(temperature).ToString()

    protected void ConvertButton_Click(object sender, EventArgs e)
{
    localhost.Convert wsConvert = new localhost.Convert();
    double temperature =
        System.Convert.ToDouble(TemperatureTextbox.Text);
    FahrenheitLabel.Text = "Fahrenheit To Celsius = " +
        wsConvert.FahrenheitToCelsius(temperature).ToString();
    CelsiusLabel.Text = "Celsius To Fahrenheit = " +
        wsConvert.CelsiusToFahrenheit(temperature).ToString();
}

  6. Press CTRL+F5 to run the page.

  7. In the text box, type a value, such as 100, and then click Convert.

    The page displays the result of converting the temperature value into both Fahrenheit and Celsius.

Debugging the Web Service

You can debug a Web service in the same way that you debug Web pages.

Note

Visual Web Developer Express and Visual Studio Standard do not support stepping into a Web service from a page that references it. If you are using Visual Web Developer Express or Visual Studio Standard, skip this section and the ones following. For more information about how to debug Web sites, see Walkthrough: Debugging Web Pages in Visual Web Developer.

To start, you must configure the Web site that contains the Web service to enable debugging.

To enable debugging in the Web services Web site

  1. On the File menu, click Open Web Site.

  2. Click Local IIS.

  3. Click TemperatureWebService, and then click Open.

  4. On the Website menu, click ASP.NET Configuration to open the Web Site Administration Tool.

    Note

    If this is the first time that you have run the Web Site Administration Tool, there might be some delay before it appears.

  5. Click Application, and then click Application Configuration.

  6. Under Debugging and Tracing, click Configure debugging and tracing.

  7. Select the Enable debugging check box.

    The Web Site Administration Tool creates a Web.config file for the Web site and sets a configuration option to enable debugging.

    Note

    To see the Web.config file in Solution Explorer, click the Web site name and then, on the Solution Explorer toolbar, click Refresh.

  8. Close the Web Site Administration Tool.

You must now enable debugging for the Web site that uses the Web service.

To enable debugging in the Web site

  1. Open the TemperatureWeb site.

  2. On the Website menu, click ASP.NET Configuration to open the Web Site Administration Tool.

  3. Click Application, click Application Configuration, under Debugging and Tracing, click Configure debugging and tracing, and then select the Enable debugging check box.

  4. Close the Web Site Administration Tool.

    Note

    To see the Web.config file in Solution Explorer, select the Web site name and then, on the Solution Explorer toolbar, click Refresh.

  5. In Solution Explorer, right-click Default.aspx, and then click View Code.

    Visual Web Developer opens the code file for the page.

  6. Position the pointer in the following line:

    temperature = System.Convert.ToDouble(TemperatureTextbox.Text)

    double temperature =
    System.Convert.ToDouble(TemperatureTextbox.Text);

  7. Press F9 to set a breakpoint on the line.

Testing Debugging

Both the Web site and the Web service are configured for debugging, so that you can now try debugging. You will start in the Default.aspx page and step through the code until the code invokes the Web service. The debugger will switch to the Web service and continue stepping through the code.

To debug the page and Web service

  1. Press F5 to run the Default.aspx page with debugging.

    The page appears in the browser.

  2. In the box, type a value, such as 100, and then click Convert.

    Visual Web Developer starts running the code for the page, but stops and highlights the line with the breakpoint on it.

  3. Press F11 to step to the next line.

  4. Press F11 again.

    Because the next line invokes the Web service, the debugger steps into the Web service, stopping on the first line of the FahrenheitToCelsius method.

  5. Continue pressing F11.

    The debugger steps through the rest of the method, and then returns to the calling page. If you continue stepping, the debugger will step back into the Web service and into the CelsiusToFahrenheit method.

  6. Close the browser, which also closes the debugger.

Next Steps

This walkthrough has illustrated the basic principles of creating a very simple Web service and using it in an ASP.NET application. You might want to experiment with additional, more complex Web service features. For more information, see:

XML Web Services in Visual FoxPro, Introduction to Programming Web Services in Managed Code, Web Services (How Do I) (Visual Basic), XML Web Services Created with ATL Server, and Creating and Accessing XML Web Services Walkthroughs.

See Also

Tasks

Walkthrough: Debugging Web Pages in Visual Web Developer

Other Resources

@ WebService

<webServices> Element