Resharper Refactor pattern for TryGetValue in Dictionary

Question

The most cumbersome piece of syntax I need to continually write is lazily initializing a container in a dictionary like:

ContainerRecord value;
if(!_dictionary.TryGetValue(key,out value))
{
   value = new ContainerRecord();
   _dictionary[key] = value;
}
//Container is always initialized here

Which I feel would be a trivial refactor pattern from: (At least for the explicit variable declaration and if statement part)

var value = _dictionary[key];

I know there is some new syntactic sugar in newer versions of C# that eliminate the need for pre-declaring out variables. Unfortunately I don't have access to these features in my environment and won't for the foreseeable future.

There does appear to be a "check for contains key" refactor, which is achieves almost the same result with the downside of doing the lookup twice.

Is this possible through some extension? I figured it is a common enough case that it would have already been solved somewhere.

Answer 1

You can create a Custom Pattern for this.

1. Open ReSharper | Options....
2. Go to the Code Inspection | Custom Patterns node.
3. Click Add pattern button.
4. Select Replace on the top right of the dialog.

5. Add the following four placeholders with the Add Placeholder button:

   Type: Identifier Placeholder
   Name: value
   
   Type: Expression Placeholder
   Name: key
   
   Type: Type Placeholder
   Name: type
   
   Type: Expression Placeholder
   Name: dict
   Expression Type: System.Collections.Generic.IDictionary<,>
   

6. Enter the following as the Search pattern in the text area on the top:

   $type$ $value$ = $dict$[$key$];
   

7. Enter the following as the Replace pattern in the text area on the bottom:

   $type$ $value$;
   if(!$dict$.TryGetValue($key$, out $value$))
   {
       $value$ = new $type$();
       $dict$[$key$] = $value$;
   }
   

8. Optional: Fill out the Description on the top. I used Replace with TryGetValue.

9. Optional: Fill out the Description on the bottom. I used the same.
10. Optional: Check the Format after replace checkbox.

The finished dialog should look like this:

11. Click on the Save button.
12. Back in the Custom Patterns, you can set the severity level for your new pattern on the right side using the dropdown. I selected Suggestion.
13. Exit the Options by clicking the Save button.

If you set up everything correctly, ReSharper should mark the matching patterns with the suggested fix: