CODEWITHSUNDEEP
c#namespaces
user3092503
user3092503

Reputation:

Is there a way to avoid redundant "using" directives when I only want to use an alias some of the time?

I've been writing a lot of code that works with Windows Forms and Excel Interop recently. One of the things that I've encountered is ambiguous references. For example, if I try to create a new Excel application, it doesn't work.

Application app = new Application { Visible = true };

This line returns an error because the reference to Application is ambiguous. It could refer to an Excel application, but it could also refer to a Windows Forms application.

Instead of typing this out:

Microsoft.Office.Interop.Excel.Application = new Microsoft.Office.Interop.Excel.Application { Visible = true };

I know I can just change my using directive to this:

using Excel = Microsoft.Office.Interop.Excel;

and then change my declaration of app to:

Excel.App app = new Excel.App { Visible = true};

However, later on in my code, I have to declare quite a few worksheets and workbooks. Without using the "Excel = Microsoft..." namespace alias, I could just do this since the references to Workbook and Worksheet aren't ambiguous:

Workbook someWorkbook = app.Workbooks.Add();
Worksheet someWorksheet = app.ActiveSheet;

But when I change my using directive to 

using Excel = Microsoft.Office.Interop.Excel;

I have to change all declarations that use Excel objects to "Excel.someObject", or I have to add a second using directive:

Option 1:

using Excel = Microsoft.Office.Interop.Excel;
...
Excel.Application app = new Application { Visible = true };
Excel.Workbook someWorkbook = app.Workbooks.Add();
Excel.Worksheet someWorkSheet = app.ActiveSheet;

Option 2:

using Excel = Microsoft.OFfice.Interop.Excel;
using Microsoft.Office.Interop.Excel;
...
Excel.Application app = new Application { Visible = true };
Workbook someWorkbook = app.Workbooks.Add();
Worksheet someWorkSheet = app.ActiveSheet;

I much prefer Option 2, and this is me being pedantic, but the redundancy of having to write two using directives to refer to the same library is irksome. Is there a third option that allows me to write my declarations as seen in option 2 without having to use two using directives? That is, is there a way to write my using directive such that the alias can be used where needed but omitted where references aren't ambiguous?

Upvotes: 1

Views: 230

Answers (2)

Sergey Kalinichenko
Sergey Kalinichenko

Reputation: 726509

If you are in a file that does not need to refer to System.Windows.Forms.Application (most files in your project should be like that), add using Microsoft.Office.Interop.Excel at the namespace level:

using System.Windows.Forms;

namespace TestForms {

    using Microsoft.Office.Interop.Excel;

    class TestClass {
        Application app = ... // This refers to Microsoft.Office.Interop.Excel.Application
    }

}

This way Microsoft.Office.Interop.Excel.Application would "win" over System.Windows.Forms.Application for all classes that follow using declaration.

Upvotes: 0

Habib
Habib

Reputation: 223237

Is there a third option that allows me to write my declarations as seen in option 2 without having to use two using statements?

No. There is not. Your best bet is to use option 2.

using directive usage for alias support is useful for specifying alias for a type or namespace.

You should look into Resharper, which could help you do the cleanup better than Visual Studio.

This problem can also be solved with a better design. Try to keep your work related to Excel in a separate class/modules, so that you can avoid conflicting namespaces issue.

Upvotes: 0

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