Chapter 19 Web Services

sef · February 13th, 2012, 06:17 PM

On page 651 Try it out there's an instruction right at number 1:
Add a new C# Windows Forms Application to the [ASP.NET] solution ...

But how?

Oops i just found out how: Add Item, New Project - C# Windows Form...
Sorry... this form you can fill in alright, but when you press 'Reverse Message' it crashes on its own non-error. This is weird, or i'm missing sth.

Code:

        void client_ReverseStringCompleted(object sender, WebServicesSample.ReverseStringCompletedEventArgs e)
        {
            if (e.Error != null)
            {
                textBox2.Text = e.Result;
            }
            else
            {
                MessageBox.Show(e.Error.Message);
            }
        }

irProject · February 14th, 2012, 01:20 AM

Hi there

if you create a new solution that contains only one project, you can't add new project from Solution Explorer. to do this from 'File' menu point to 'Add Project...' and continue.

ChristianNagel · February 14th, 2012, 09:06 AM

Quote:

Originally Posted by irProject

Hi there

if you create a new solution that contains only one project, you can't add new project from Solution Explorer. to do this from 'File' menu point to 'Add Project...' and continue.

This depends on your project settings. If you have a C# configuration (Tools -> Import and Export Settings -> Reset all settings), the solution explorer shows the solution, and you can add projects. If you have other settings configured (VB, Web...), with only one project the solution explorer just shows the project.

Hope this helps.

ChristianNagel · February 14th, 2012, 09:11 AM

Quote:

Originally Posted by sef

On page 651 Try it out there's an instruction right at number 1:
Add a new C# Windows Forms Application to the [ASP.NET] solution ...

But how?

Oops i just found out how: Add Item, New Project - C# Windows Form...
Sorry... this form you can fill in alright, but when you press 'Reverse Message' it crashes on its own non-error. This is weird, or i'm missing sth.

Code:

        void client_ReverseStringCompleted(object sender, WebServicesSample.ReverseStringCompletedEventArgs e)
        {
            if (e.Error != null)
            {
                textBox2.Text = e.Result;
            }
            else
            {
                MessageBox.Show(e.Error.Message);
            }
        }

You need to change the expression of the if statement:

Code:

  if (e.Error == null)
  {
    textBox2.Text = e.Result;
  }
  else
  {
    MessageBox.Show(e.Error.Message);
  }

In the first Version when there was no error and e.Error is null, the else clause is Happening where the Error property is accessed. Because the Error property is null, there's a NullReferenceException accessing the Message property.