特定字典项的C# MemberExpression

using System;
using System.Collections.Generic;
using System.Linq.Expressions;

class Program
{
    static void Main()
    {
        Dictionary<string, int> dictionary = new Dictionary<string, int>()
        {
            { "apple", 1 },
            { "banana", 2 },
            { "orange", 3 }
        };

        string keyToAccess = "banana";

        // 创建表示字典的参数表达式
        ParameterExpression dictionaryParameter = Expression.Parameter(typeof(Dictionary<string, int>), "dictionary");

        // 创建表示字典键的常量表达式
        ConstantExpression keyExpression = Expression.Constant(keyToAccess);

        // 创建表示字典访问的MemberExpression
        MemberExpression memberExpression = Expression.Property(dictionaryParameter, "Item", keyExpression);

        // 创建表示访问字典值的Lambda表达式
        Expression<Func<Dictionary<string, int>, int>> lambdaExpression = Expression.Lambda<Func<Dictionary<string, int>, int>>(memberExpression, dictionaryParameter);

        // 编译Lambda表达式并执行
        Func<Dictionary<string, int>, int> getValue = lambdaExpression.Compile();
        int value = getValue(dictionary);

        Console.WriteLine($"The value of key '{keyToAccess}' is {value}.");
    }
}