MutatR

Single .tt file to auto generate immutable class mutation methods

How to use

1. Just copy MutatR.tt into project file, you want to modify, no matter at which location there (for example project's root). Then specify CustomTooloption in file properties as TextTemplatingFileGenerator, which allow T4 processor to generate code follow this template. Anyway, at this moment impossible to generate code using outside of MS VisualStudio, due to some limitation of resolving project items with T4.
2. Mark any classes, designed to be immutable with MutatR.ImmutableAttribute and make them partial keyword which enables lookup them by generator and extending their functionality outside.
3. Execute Run Custom Tool action on MutatR.tt (Right click on MutatR.tt) to regenarate mutation infrastructure for classes.
4. Use it! Just call Mutate() on class instance to begin mutation process, then you can to use generated With*(value) methods in fluent manner to change values of related fields and properties, after that call Commit() to receive updated copy of your object.

Example

namespace MutatR.Demo
{
    [MutatR.Immutable]
    internal partial class ImmutableTest
    {
        #region Fields

        public readonly double DoubleField;
        public readonly int IntField;
        public readonly string StringField;

        #endregion

        #region Properties

        public double DoubleProperty { get; }
        public int IntProperty { get; }
        public string StringProperty { get; }

        #endregion

        #region Constructors

        public ImmutableTest()
        {
        }

        #endregion
    }
    
    internal class Program
    {
        #region Methods

        private static void Main(string[] args)
        {
            var immutableTest1 = new ImmutableTest();
            var immutableTest2 = immutableTest1.Mutate()
                                               .WithDoubleField(1.0)
                                               .WithIntField(1)
                                               .WithStringField("1")
                                               .WithDoubleProperty(2.0)
                                               .Commit();
        }

        #endregion
    }
}