C#, 利用dynamic宣告變數

利用dynamic宣告變數

using System;
class Program
{
    static void Main()
    {
        // 宣告 dynamic 物件
        dynamic dynamicObject = new { Property1 = "Value1", Property2 = 42, Property3 = true };
        // 取得屬性值
        string value1 = dynamicObject.Property1;
        int value2 = dynamicObject.Property2;
        bool value3 = dynamicObject.Property3;
        // 顯示取得的值
        Console.WriteLine($"Property1: {value1}");
        Console.WriteLine($"Property2: {value2}");
        Console.WriteLine($"Property3: {value3}");
    }
}

利用dynamic宣告空的變數, 動態指定屬性資料

using System;
class Program
{
    static void Main()
    {
        // 宣告 dynamic 變數
        dynamic dynamicObject = new System.Dynamic.ExpandoObject();
        // 給動態變數不同的屬性名稱和值
        dynamicObject.Property1 = "Value1";
        dynamicObject.Property2 = 42;
        dynamicObject.Property3 = true;
        // 讀取動態變數的屬性
        string value1 = dynamicObject.Property1;
        int value2 = dynamicObject.Property2;
        bool value3 = dynamicObject.Property3;
        // 顯示讀取的值
        Console.WriteLine($"Property1: {value1}");
        Console.WriteLine($"Property2: {value2}");
        Console.WriteLine($"Property3: {value3}");
    }
}

缺點 : 使用dynamic變數時, 打"點"之後不會自動顯示可用屬性, 需手動輸入屬性名稱

dynamic變數跨類別後, 就無法直接取得屬性值

(在偵錯模式雖然看得到值, 但讀取時會顯示無此屬性), 這時可以使用Reflection來取得屬性名稱。

public static object GetDynamicValue(string PropertyName, dynamic dynData )
{
    object o = null;
    Type type = dynData.GetType();
    //取得集合(List)內的型別
    PropertyInfo[] classProperties = type.GetProperties();
    foreach (PropertyInfo property in classProperties)
    {
        if (property.Name == PropertyName)
        {
            o = property.GetValue(dynData);
            break;
        }
    }
    return o;
}
public static Main()
{
    dynamic obj = new { p1 = "123", p2 = 456};
    
    string p1Value = GetDynamicValue("p1", obj);  //p1Value="123"
}

也可以轉個彎, 先把dynamic object轉為JSon格式字串, 使用string方式傳到方法內, 再反轉回dynamic Object, 這時dynamic Object就可以直接使用屬性取得值

反序列化(JSON字串轉C# Class)

using Newtonsoft.Json;
class Program
{
    static void Main()
    {
        string jsonString = @"
        [
            {""Name"":""John"",""Country"":""USA"",""Age"":25},
            {""Name"":""Alice"",""Country"":""Canada"",""Age"":30},
            {""Name"":""Bob"",""Country"":""UK"",""Age"":22}
        ]";
        // 反序列化為 List<MyClass>
        var myObjects = JsonConvert.DeserializeObject<List<MyClass>>(jsonString);
        // 輸出結果
        foreach (var obj in myObjects)
        {
            Console.WriteLine($"姓名: {obj.Name}, 國家: {obj.Country}, 年紀: {obj.Age}");
        }
    }
}

序列化(C# Class轉JSON字串)

using Newtonsoft.Json;

class Program
{
    static void Main()
    {
        List<MyClass> myObjects = new List<MyClass>
        {
            new MyClass { Name = "John", Country = "USA", Age = 25 },
            new MyClass { Name = "Alice", Country = "Canada", Age = 30 },
            new MyClass { Name = "Bob", Country = "UK", Age = 22 }
        };

        // 序列化為 JSON 字符串
        string jsonString = JsonConvert.SerializeObject(myObjects, Formatting.Indented);

        // 輸出結果
        Console.WriteLine(jsonString);
    }
}