如何解决DynamoDB报错：参数2无法从DynamoDBOperationConfig转为AmazonDynamoDBCallback

我正在使用DynamoDB进行开发，项目中需要动态设置数据库表名并动态加载数据库，以下是我的代码：

using UnityEngine;
using System.Collections;
using Amazon.DynamoDBv2.DataModel;
using System.Collections.Generic;
using Amazon.DynamoDBv2;
using UnityEngine.UI;
using UnityEngine;
using System.Collections;
using Amazon.DynamoDBv2;
using UnityEngine.UI;
using Amazon;

namespace AWSSDK.Examples
{
public class HighLevel3 : DynamoDbBaseExample
{

    private IAmazonDynamoDB _client;
    private DynamoDBContext _context;

    public Text resultText;
    public Button back;
    public Button createOperation;
    public Button updateOperation;
    public Button deleteOperation;
    public string S_tablefieldset;
    string bookID;
    int bookID1 = 9;
    public string Email;

    private DynamoDBContext Context
    {
        get
        {
            if (_context == null)
                _context = new DynamoDBContext(_client);

            return _context;
        }
    }

    void Awake()
    {
        
        back.onClick.AddListener(BackListener);
        createOperation.onClick.AddListener(PerformCreateOperation);
        _client = Client;
        S_tablefieldset = "Orders";
        HighLevelTableExample.GetDynamoDbOperationConfig(S_tablefieldset);

    }

    void Start()
    {
        bookID = SystemInfo.deviceUniqueIdentifier;
        System.Environment.SetEnvironmentVariable("MONO_REFLECTION_SERIALIZER", "Orders");
        PerformCreateOperation();
    }


    public static DynamoDBOperationConfig GetDynamoDbOperationConfig(string dynamoDbTable)
    {
        Debug.Log("The Table name is " + dynamoDbTable);
        var tableName = System.Environment.GetEnvironmentVariable("MONO_REFLECTION_SERIALIZER");
        Debug.Log("The Table name is" + tableName);
        DynamoDBOperationConfig config = new DynamoDBOperationConfig()
        {
            OverrideTableName = tableName
        };

        return config;
    }

      public void PerformCreateOperation()
    {
        Debug.Log(" I am in Perform Create Operation is working fine and good");
        Book12 myBook = new Book12
        {
            OrderID = bookID,
            OrderItem = 50,
           
        };

        // Save the book.
        var tableName = System.Environment.GetEnvironmentVariable("TABLE_NAME");
        Context.SaveAsync(myBook, new DynamoDBOperationConfig {

      OverrideTableName = tableName });
                
    }
}

public class Book12
{
    [DynamoDBHashKey]   // Hash key.
    public string  OrderID { get; set; }
    [DynamoDBProperty]
    public string UserName { get; set; }
    [DynamoDBProperty]
    public int OrderItem { get; set; }
}

error CS1503: Argument 2: cannot convert from 'Amazon.DynamoDBv2.DataModel.DynamoDBOperationConfig' to Amazon.DynamoDBv2.AmazonDynamoDBCallback'

错误原因是SaveAsync方法的参数顺序传错：AWS .NET SDK中DynamoDBContext.SaveAsync的非await重载，第二个参数要求传入回调委托，你直接把DynamoDBOperationConfig放在第二个参数位，类型不匹配触发报错。同时你的代码存在隐性问题：Start方法中给MONO_REFLECTION_SERIALIZER环境变量赋值，但是读取时用的环境变量名是TABLE_NAME，会读不到有效值。

修复步骤如下：

1. 先统一环境变量名，修改Start方法中的赋值逻辑：

void Start()
{
    bookID = SystemInfo.deviceUniqueIdentifier;
    // 统一环境变量名，和读取时保持一致
    System.Environment.SetEnvironmentVariable("TABLE_NAME", "Orders");
    PerformCreateOperation();
}

2. 修正SaveAsync的传参，根据需求选择以下任意一种写法：

• 不需要回调的写法，第二个参数传null即可：

Context.SaveAsync(myBook, null, new DynamoDBOperationConfig 
{
    OverrideTableName = tableName 
});

• 需要监听保存结果的写法，传入对应回调：

Context.SaveAsync(myBook, (AmazonDynamoDBResult<object> result) => 
{
    if(result.Exception != null)
    {
        Debug.LogError("数据保存失败：" + result.Exception.Message);
        return;
    }
    Debug.Log("数据保存成功");
}, new DynamoDBOperationConfig 
{
    OverrideTableName = tableName 
});

• 若你的SDK版本支持Task异步，可直接用await写法，不用额外传回调：

// 方法标记为async
public async void PerformCreateOperation()
{
    // 原有逻辑不变
    await Context.SaveAsync(myBook, new DynamoDBOperationConfig 
    {
        OverrideTableName = tableName 
    });
}

内容的提问来源于stack exchange，提问作者karthik keyan