Tutorial: Accessing web services from Microsoft .NET

The following tutorial demonstrates how to access web services from Microsoft .NET using Visual C#.

To create SOAP and DISH services

At a command prompt, run the following command to start a personal web server. Replace samples-dir with the actual location of the sample database. The -xs http(port=80) option tells the database server to accept HTTP requests on port 80. If you already have a web server running on port 80, use another port number such as 8080 for this tutorial and use 8080 instead of 80 in all port references.
dbeng11 -xs http(port=80) samples-dir\demo.db

Start Interactive SQL. Connect to the SQL Anywhere sample database as the DBA. Execute the following statements:

Define a SOAP service that lists the Employees table.

CREATE SERVICE "SASoapTest/EmployeeList"
TYPE 'SOAP'
AUTHORIZATION OFF
SECURE OFF
USER DBA
AS SELECT * FROM Employees;

Because authorization has been turned off, anyone can use this service without supplying a user name and password. The commands run under user DBA. This arrangement is simple, but insecure.

Create a DISH service to act as a proxy for the SOAP service and to generate the WSDL document.

CREATE SERVICE "SASoapTest_DNET"
TYPE 'DISH'
GROUP "SASoapTest"
FORMAT 'DNET'
AUTHORIZATION OFF
SECURE OFF
USER DBA;

The SOAP and DISH service must be of format DNET. In this example, the FORMAT clause was omitted when the SOAP service was created. As a result, the SOAP service inherits the DNET format from the DISH service.

Start Microsoft Visual Studio. Note that this example uses functions from the .NET Framework 2.0.

Create a new Windows application project using Visual C#.

An empty form appears.
From the Project menu, choose Add Web Reference.
In the URL field of the Add Web Reference page, enter the following URL: http://localhost:80/demo/SASoapTest_DNET.
Click Go.

You are presented with a list of the methods available for SASoapTest_DNET. You should see the EmployeeList method.
Click Add Reference to finish.

The Solution Explorer window shows the new web reference.
From the Visual Studio Toolbox, add a listbox and a button to the form as shown in the following diagram.
Rename the button text to Employee List.

Double-click Employee List and add the following code for the button click event.

int sqlCode;

listBox1.Items.Clear();

localhost.SASoapTest_DNET proxy = new localhost.SASoapTest_DNET();

DataSet results = proxy.EmployeeList(out sqlCode);
DataTableReader dr = results.CreateDataReader();
while (dr.Read())
{
  for (int i = 0; i < dr.FieldCount; i++)
  {
    string columnName = dr.GetName(i);
    try
    {
      string value = dr.GetString(i);
      listBox1.Items.Add(columnName + "=" + value);
    }
    catch ( InvalidCastException )
    {
      listBox1.Items.Add(columnName + "=(null)");
    }
  }
  listBox1.Items.Add("");
}
dr.Close();

Build and run the program.

The listbox will display the EmployeeList result set as column name=value pairs.

A try/catch block is included to handle NULL column values such as those found in the TerminationDate column of the Employees table.

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