Utilities

AccessTools

To simplify reflections, Harmony has a helper class called AccessTools. Here are the most commonly used methods:

public static BindingFlags all = ....
public static Type TypeByName(string name)
public static FieldInfo Field(Type type, string name)
public static PropertyInfo Property(Type type, string name)
public static MethodInfo Method(Type type, string name, Type[] parameters = null, Type[] generics = null)
public static ConstructorInfo Constructor(Type type, Type[] parameters = null)
public static Type Inner(Type type, string name)
public static Type FirstInner(Type type, Func<Type, bool> predicate)

Any of these methods use the all BindingFlags definition and thus work on anything regardless if it is public, private, static or else.

Traverse

In order to access fields, properties and methods from classes via reflection, Harmony contains a utility called Traverse. Think of it as LINQ for classes. Here are the main methods:

// starting from a type or instance
public static Traverse Create(Type type)
public static Traverse Create<T>()
public static Traverse CreateWithType(string name)

// digging deeper
public Traverse Type(string name)
public Traverse Field(string name)
public Traverse Property(string name, object[] index = null)
public Traverse Method(string name, params object[] arguments)
public Traverse Method(string name, Type[] paramTypes, object[] arguments = null)

// calling getter or method
public object GetValue()
public T GetValue<T>()
public object GetValue(params object[] arguments)
public T GetValue<T>(params object[] arguments)
public override string ToString()

// calling setter
public Traverse SetValue(object value)

// iterating
public static void IterateFields(object source, Action<Traverse> action)
public static void IterateFields(object source, object target, Action<Traverse, Traverse> action)
public static void IterateProperties(object source, Action<Traverse> action)
public static void IterateProperties(object source, object target, Action<Traverse, Traverse> action)

Example:

class Foo
{
    struct Bar
    {
        static string secret = "hello";

        public string ModifiedSecret() => secret.ToUpper();
    }

    Bar MyBar
    {
        get
        {
            return new Bar();
        }
    }

    public string GetSecret() => MyBar.ModifiedSecret();

    Foo()
    {
    }

    static Foo MakeFoo() => new();
}

void Test()
{
    var foo = Traverse.Create<Foo>().Method("MakeFoo").GetValue<Foo>();
    Traverse.Create(foo).Property("MyBar").Field("secret").SetValue("world");
    Console.WriteLine(foo.GetSecret()); // outputs WORLD
}

Although most fields, properties and methods in that class hierarchy are private, Traverse can easily access anything. It has build-in null protection and propagates null as a result if any of the intermediates would encounter null. It works with static types and caches lookups which makes it pretty fast.

FileLog

For simple and quick logging, Harmony uses a tool class FileLog. It has three methods:

public static void Log(string str)
// Creates a new log file called "harmony.log.txt" on the computers Desktop (if it not already exists) and appends *str* to it. 

public static void Reset()
// Deletes the log file.

public static unsafe void LogBytes(long ptr, int len)
// Same as Log(string str) but logs a hex dump and md5 hash.