Transform Parameters refactoring

This refactoring helps you quickly change method signature by transforming parameters — for example, get rid of out parameters, wrap parameters in a tuple or in a new class, and so on. — and automatically update all usages of the method in your solution.

The refactoring lets you perform the following transformations:

Encapsulate input parameters into a parameter object. The refactoring will create a new class with public fields or auto-properties corresponding to the selected input parameters.
Encapsulate return values and out parameters into a return object. The refactoring will create a tuple or a new class with public fields or auto-properties corresponding to the selected return components and output parameters.
Transform some of the return tuple components to out parameters and vice versa. The refactoring will extend the return tuple with the selected output values and create out parameters from unselected ones.
Encapsulate the input part of a ref parameter into a parameter object. The refactoring will replace the modifier with out for the unselected output values that correspond to ref parameters.
Encapsulate the output part of a ref parameter into a return tuple or object. The refactoring will remove the modifier for the unselected input values that correspond to ref parameters.
Encapsulate parameters and return values into a single parameter object. The refactoring will create additional writable fields or properties for return values that correspond to the selected return components and out parameters.

The example below demonstrates a mix of transformations — we replace out parameter with method return, and we wrap two other parameters with a new class:

            
class TestClass
{
  public void DrawCircle(Point ctr, float rad, out bool res)
  {
    // draw...
    res = true;
  }
}

        

            
class TestClass
{
  public bool DrawCircle(Circle circle)
  {
    // draw... .
    var res = true;
    return res;
  }
}

internal class Circle
{
  public Circle(Point ctr, float rad)
  {
    Ctr = ctr;
    Rad = rad;
  }

  public Point Ctr { get; private set; }
  public float Rad { get; private set; }
}

        

Transform method parameters

Place the caret at the declaration or a usage of method in the editor, or select the method in the Structure window window. Or, alternatively, place the caret at any of method parameters.
Do one of the following:
- Press Alt+Enter and choose Transform Parameters.
- Press Ctrl+Alt+Shift+T and then choose Transform Parameters.
- Choose Refactor | Transform Parameters from the main menu.
The Transform Parameters dialog will open.
Select parameters you want to transform.
Depending on selected in/out parameters, JetBrains Rider enables Method receives and/or Method returns selectors. Use these selectors to choose how in/out parameters should be transformed. If you choose to create a new class for parameters, you will be able to specify its name in a field to the right of it.
To apply the refactoring, click Next.
If no conflicts are found, JetBrains Rider performs the refactoring immediately. Otherwise, it prompts you to resolve conflicts.
Right after the refactoring has been completed, all changes that it makes anywhere, including other files, are registered as a single operation. So you can use the Undo action Ctrl+Z to roll back all these changes with a single keystroke.

JetBrains Rider. Transforming method's parameters

06 February 2025