What is BaseDefinition and ContentType in visual studio extension development

Question

I have been looking into this example Walkthrough: Customize the text view

In this example, the content type is text as shown here.

[Export(typeof(IWpfTextViewCreationListener))]

[ContentType("text")]

[TextViewRole(PredefinedTextViewRoles.Document)]

internal class TestViewCreationListener : IWpfTextViewCreationListener

Mine is a CSharp file, so I tried changing from text to code. But did not work, not sure why.

In various examples on github I have seen, different types.

For example this Ook example uses code

This Diff Classifier example uses text

And in the same file, you can see diff as well if you scroll down a bit(line 30).

So when to use what? What are the different values that this can take? Any arbitrary string value?

Am trying to understand Link a content type to a file name extension example

A quick search on github showed many different things.

Like here I saw intellisence, json here, html here and so on.

So what are the sensible values for BaseDefinition and ContentType?

And what does BaseDefinitionAttribute represent in the first place?

The pain is documentation is very poor, you can see it here for ContentTypes.

Answer 1

Brief Explanation with Examples:

1. ContentType:

• Indicates the type of content your extension targets (e.g., text, code, html, json).
• Example:

csharp
1[Export(typeof(IWpfTextViewCreationListener))]
2[ContentType("text")] // Targets plain text files
3[TextViewRole(PredefinedTextViewRoles.Document)]
4internal class TestViewCreationListener : IWpfTextViewCreationListener

For programming files, use ContentType("code") or specify types like "CSharp" for C# files.

---

2. BaseDefinition:

• Establishes a hierarchy among content types (e.g., "CSharp" is derived from "code").
• Example:

csharp
1[Export]
2[Name("MyCustomContentType")]
3[BaseDefinition("code")] // Custom type inherits from "code"
4internal static ContentTypeDefinition CustomContentTypeDefinition { get; }

This allows MyCustomContentType to inherit properties and behaviors from the "code" type.

---

When to Use:

• Use "text" for generic text files, "code" for programming files, and specific types like "html" or "CSharp" for specialized cases.
• If "code" does not apply, use the precise type (e.g., "CSharp" for C# files). Brief Explanation with Examples:
  1. ContentType:
     • Indicates the type of content your extension targets (e.g., text, code, html, json).
       • Example:

               csharp
               1[Export(typeof(IWpfTextViewCreationListener))]
       

2[ContentType("text")] // Targets plain text files 3[TextViewRole(PredefinedTextViewRoles.Document)] 4internal class TestViewCreationListener : IWpfTextViewCreationListener

    ```

    
    For programming files, use **`ContentType("code")`** or specify types like **`"CSharp"`** for C# files.
```  2. BaseDefinition:
  
     - Establishes a hierarchy among content types (e.g., **`"CSharp"`** is derived from **`"code"`**).
     
        - **Example:**
        
        ```
        csharp
        1[Export]
2[Name("MyCustomContentType")]
3[BaseDefinition("code")] // Custom type inherits from "code"
4internal static ContentTypeDefinition CustomContentTypeDefinition { get; }

```


This allows **`MyCustomContentType`** to inherit properties and behaviors from the **`"code"`** type.

  
  - Use **`"text"`** for generic text files, **`"code"`** for programming files, and specific types like **`"html"`** or **`"CSharp"`** for specialized cases.
  
- If **`"code"`** does not apply, use the precise type (e.g., **`"CSharp"`** for C# files).