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238 lines
12 KiB
238 lines
12 KiB
using System;
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using System.Collections.Generic;
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using System.Reflection;
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using System.Reflection.Emit;
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namespace IPA.Utilities
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{
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/// <summary>
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/// A type containing utilities for accessing non-public fields of objects.
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/// </summary>
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/// <typeparam name="T">the type that the fields are on</typeparam>
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/// <typeparam name="U">the type of the field to access</typeparam>
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/// <seealso cref="PropertyAccessor{T, U}"/>
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public static class FieldAccessor<T, U>
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{
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/// <summary>
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/// A delegate for a field accessor taking a <typeparamref name="T"/> ref and returning a <typeparamref name="U"/> ref.
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/// </summary>
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/// <param name="obj">the object to access the field of</param>
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/// <returns>a reference to the field's value</returns>
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public delegate ref U Accessor(ref T obj);
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// field name -> accessor
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private static readonly Dictionary<string, Accessor> accessors = new Dictionary<string, Accessor>();
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private static Accessor MakeAccessor(string fieldName)
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{
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var field = typeof(T).GetField(fieldName, BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance | BindingFlags.DeclaredOnly);
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if (field == null)
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throw new MissingFieldException(typeof(T).Name, fieldName);
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var dynMethodName = $"<>_accessor__{fieldName}";
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// unfortunately DynamicMethod doesn't like having a ByRef return type, so reflection it
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var dyn = new DynamicMethod(dynMethodName, typeof(U), new[] { typeof(T).MakeByRefType() }, typeof(FieldAccessor<T, U>), true);
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ReflectionUtil.DynamicMethodReturnType.SetValue(dyn, typeof(U).MakeByRefType());
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var il = dyn.GetILGenerator();
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il.Emit(OpCodes.Ldarg_0);
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if (!typeof(U).IsValueType)
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il.Emit(OpCodes.Ldind_Ref);
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il.Emit(OpCodes.Ldflda, field);
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il.Emit(OpCodes.Ret);
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return (Accessor)dyn.CreateDelegate(typeof(Accessor));
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}
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/// <summary>
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/// Gets an <see cref="Accessor"/> for the field named <paramref name="name"/> on <typeparamref name="T"/>.
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/// </summary>
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/// <param name="name">the field name</param>
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/// <returns>an accessor for the field</returns>
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/// <exception cref="MissingFieldException">if the field does not exist on <typeparamref name="T"/></exception>
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public static Accessor GetAccessor(string name)
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{
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if (!accessors.TryGetValue(name, out var accessor))
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accessors.Add(name, accessor = MakeAccessor(name));
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return accessor;
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}
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/// <summary>
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/// Accesses a field for an object by name.
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/// </summary>
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/// <param name="obj">the object to access the field of</param>
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/// <param name="name">the name of the field to access</param>
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/// <returns>a reference to the object at the field</returns>
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/// <exception cref="MissingFieldException">if the field does not exist on <typeparamref name="T"/></exception>
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/// <seealso cref="GetAccessor(string)"/>
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public static ref U Access(ref T obj, string name) => ref GetAccessor(name)(ref obj);
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/// <summary>
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/// Gets the value of a field of an object by name.
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/// </summary>
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/// <remarks>
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/// The only good reason to use this over <see cref="Get(T, string)"/> is when you are working with a value type,
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/// as it prevents a copy.
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/// </remarks>
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/// <param name="obj">the object to access the field of</param>
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/// <param name="name">the name of the field to access</param>
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/// <returns>the value of the field</returns>
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/// <exception cref="MissingFieldException">if the field does not exist on <typeparamref name="T"/></exception>
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/// <seealso cref="Get(T, string)"/>
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/// <seealso cref="Access(ref T, string)"/>
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/// <seealso cref="GetAccessor(string)"/>
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public static U Get(ref T obj, string name) => Access(ref obj, name);
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/// <summary>
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/// Gets the value of a field of an object by name.
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/// </summary>
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/// <param name="obj">the object to access the field of</param>
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/// <param name="name">the name of the field to access</param>
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/// <returns>the value of the field</returns>
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/// <exception cref="MissingFieldException">if the field does not exist on <typeparamref name="T"/></exception>
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/// <seealso cref="Get(ref T, string)"/>
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/// <seealso cref="Access(ref T, string)"/>
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/// <seealso cref="GetAccessor(string)"/>
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public static U Get(T obj, string name) => Get(ref obj, name);
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/// <summary>
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/// Sets the value of a field for an object by name.
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/// </summary>
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/// <remarks>
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/// This overload must be used for value types.
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/// </remarks>
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/// <param name="obj">the object to set the field of</param>
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/// <param name="name">the name of the field</param>
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/// <param name="value">the value to set it to</param>
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/// <exception cref="MissingFieldException">if the field does not exist on <typeparamref name="T"/></exception>
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/// <seealso cref="Set(T, string, U)"/>
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/// <seealso cref="Access(ref T, string)"/>
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/// <seealso cref="GetAccessor(string)"/>
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public static void Set(ref T obj, string name, U value) => Access(ref obj, name) = value;
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/// <summary>
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/// Sets the value of a field for an object by name.
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/// </summary>
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/// <remarks>
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/// This overload cannot be safely used for value types. Use <see cref="Set(ref T, string, U)"/> instead.
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/// </remarks>
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/// <param name="obj">the object to set the field of</param>
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/// <param name="name">the name of the field</param>
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/// <param name="value">the value to set it to</param>
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/// <exception cref="MissingFieldException">if the field does not exist on <typeparamref name="T"/></exception>
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/// <seealso cref="Set(ref T, string, U)"/>
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/// <seealso cref="Access(ref T, string)"/>
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/// <seealso cref="GetAccessor(string)"/>
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public static void Set(T obj, string name, U value) => Set(ref obj, name, value);
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}
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/// <summary>
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/// A type containing utilities for accessing non-public properties of an object.
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/// </summary>
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/// <typeparam name="T">the type that the properties are on</typeparam>
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/// <typeparam name="U">the type of the property to access</typeparam>
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public static class PropertyAccessor<T, U>
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{
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/// <summary>
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/// A getter for a property.
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/// </summary>
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/// <param name="obj">the object it is a member of</param>
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/// <returns>the value of the property</returns>
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public delegate U Getter(T obj);
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/// <summary>
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/// A setter for a property.
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/// </summary>
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/// <param name="obj">the object it is a member of</param>
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/// <param name="val">the new property value</param>
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public delegate void Setter(T obj, U val);
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private static readonly Dictionary<string, (Getter get, Setter set)> props = new Dictionary<string, (Getter get, Setter set)>();
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private static (Getter, Setter) MakeAccessors(string propName)
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{
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var prop = typeof(T).GetProperty(propName, BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance | BindingFlags.DeclaredOnly);
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if (prop == null)
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throw new MissingMemberException(typeof(T).Name, propName);
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var getM = prop.GetGetMethod(true);
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var setM = prop.GetSetMethod(true);
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Getter getter = null;
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Setter setter = null;
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if (getM != null)
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getter = (Getter)Delegate.CreateDelegate(typeof(Getter), getM);
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if (setM != null)
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setter = (Setter)Delegate.CreateDelegate(typeof(Setter), setM);
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return (getter, setter);
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}
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private static (Getter get, Setter set) GetAccessors(string propName)
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{
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if (!props.TryGetValue(propName, out var access))
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props.Add(propName, access = MakeAccessors(propName));
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return access;
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}
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/// <summary>
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/// Gets a <see cref="Getter"/> for the property identified by <paramref name="name"/>.
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/// </summary>
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/// <param name="name">the name of the property</param>
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/// <returns>a <see cref="Getter"/> that can access that property</returns>
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/// <exception cref="MissingMemberException">when the property does not exist</exception>
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public static Getter GetGetter(string name) => GetAccessors(name).get;
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/// <summary>
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/// Gets a <see cref="Setter"/> for the property identified by <paramref name="name"/>.
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/// </summary>
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/// <param name="name">the name of the property</param>
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/// <returns>a <see cref="Setter"/> that can access that property</returns>
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/// <exception cref="MissingMemberException">when the property does not exist</exception>
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public static Setter GetSetter(string name) => GetAccessors(name).set;
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/// <summary>
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/// Gets the value of the property identified by <paramref name="name"/> on <paramref name="obj"/>.
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/// </summary>
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/// <remarks>
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/// The only reason to use this over <see cref="Get(T, string)"/> is if you are using a value type because
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/// it avoids a copy.
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/// </remarks>
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/// <param name="obj">the instance to access</param>
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/// <param name="name">the name of the property</param>
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/// <returns>the value of the property</returns>
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/// <exception cref="MissingMemberException">when the property does not exist</exception>
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/// <seealso cref="Get(T, string)"/>
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/// <seealso cref="GetGetter(string)"/>
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public static U Get(ref T obj, string name) => GetGetter(name)(obj);
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/// <summary>
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/// Gets the value of the property identified by <paramref name="name"/> on <paramref name="obj"/>.
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/// </summary>
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/// <param name="obj">the instance to access</param>
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/// <param name="name">the name of the property</param>
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/// <returns>the value of the property</returns>
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/// <exception cref="MissingMemberException">when the property does not exist</exception>
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/// <seealso cref="Get(ref T, string)"/>
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/// <seealso cref="GetGetter(string)"/>
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public static U Get(T obj, string name) => GetGetter(name)(obj);
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/// <summary>
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/// Sets the value of the property identified by <paramref name="name"/> on <paramref name="obj"/>.
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/// </summary>
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/// <remarks>
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/// This overload must be used for value types.
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/// </remarks>
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/// <param name="obj">the instance to access</param>
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/// <param name="name">the name of the property</param>
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/// <param name="val">the new value of the property</param>
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/// <exception cref="MissingMemberException">when the property does not exist</exception>
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/// <seealso cref="Set(T, string, U)"/>
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/// <seealso cref="GetSetter(string)"/>
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public static void Set(ref T obj, string name, U val) => GetSetter(name)(obj, val);
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/// <summary>
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/// Sets the value of the property identified by <paramref name="name"/> on <paramref name="obj"/>.
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/// </summary>
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/// <remarks>
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/// This overload cannot be safely used for value types. Use <see cref="Set(ref T, string, U)"/> instead.
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/// </remarks>
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/// <param name="obj">the instance to access</param>
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/// <param name="name">the name of the property</param>
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/// <param name="val">the new value of the property</param>
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/// <exception cref="MissingMemberException">when the property does not exist</exception>
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/// <seealso cref="Set(ref T, string, U)"/>
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/// <seealso cref="GetSetter(string)"/>
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public static void Set(T obj, string name, U val) => GetSetter(name)(obj, val);
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}
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}
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