tldr：无法从queryAsync或scanasync创建一个asyncsearch对象，而不会遇到AWS库中深处的怪异参数nullexception。
我正在开发Unity的在线游戏，并希望将数据与DynamoDB同步。当我只有一个带有播放器数据的表格时，这效果很好。我只会使用" dbcontext.loadasync（id，callback）;"而且它可以完美地发挥作用。用" saveAsync"保存也有效。
现在我介绍了更多表，需要进行扫描和查询。出于测试目的，我给了我的Unity应用程序所有可能具有的所有权利（我使用了" dynamodb：*"one_answers"资源"：["*"]。
）。我基本上尝试了具有不同参数的ScanAsync，QueryAsync和FromqueryAsync的所有可能版本，但我总是会出现错误。
简单示例：我想下载（我的大学的所有部门）：
AsyncSearch<DepartmentData> search = AWSManager.Instance.DBContext.ScanAsync<DepartmentData>();
这个呼叫已经失败了，然后才能执行诸如" search.getRemainingasync（parkback）"之类的事情。简单查询也是如此：
AsyncSearch<POIVisit> query = AWSManager.Instance.DBContext.QueryAsync<POIVisit>(poiType);
错误是以下内容，并且在AWS库中的某个地方，所以我无法真正进入那里，设置一些断点，看看到底是什么是失败的：
ArgumentNullException: Argument cannot be null.
Parameter name: key
System.Collections.Generic.Dictionary`2[System.Type,Amazon.Runtime.IExceptionHandler].TryGetValue (System.Type key, IExceptionHandler& value) (at /Users/builduser/buildslave/mono/build/mcs/class/corlib/System.Collections.Generic/Dictionary.cs:588)
Amazon.Runtime.Internal.ErrorHandler.ProcessException (IExecutionContext executionContext, System.Exception exception) (at E:/JenkinsWorkspaces/v3-trebuchet-release/AWSDotNetPublic/sdk/src/Core/Amazon.Runtime/Pipeline/ErrorHandler/ErrorHandler.cs:202)
Amazon.Runtime.Internal.ErrorHandler.InvokeSync (IExecutionContext executionContext) (at E:/JenkinsWorkspaces/v3-trebuchet-release/AWSDotNetPublic/sdk/src/Core/Amazon.Runtime/Pipeline/ErrorHandler/ErrorHandler.cs:78)
Amazon.Runtime.Internal.PipelineHandler.InvokeSync (IExecutionContext executionContext) (at E:/JenkinsWorkspaces/v3-trebuchet-release/AWSDotNetPublic/sdk/src/Core/Amazon.Runtime/Pipeline/PipelineHandler.cs:57)
Amazon.Runtime.Internal.CallbackHandler.InvokeSync (IExecutionContext executionContext) (at E:/JenkinsWorkspaces/v3-trebuchet-release/AWSDotNetPublic/sdk/src/Core/Amazon.Runtime/Pipeline/Handlers/CallbackHandler.cs:45)
Amazon.Runtime.Internal.PipelineHandler.InvokeSync (IExecutionContext executionContext) (at E:/JenkinsWorkspaces/v3-trebuchet-release/AWSDotNetPublic/sdk/src/Core/Amazon.Runtime/Pipeline/PipelineHandler.cs:57)
Amazon.Runtime.Internal.Signer.InvokeSync (IExecutionContext executionContext) (at E:/JenkinsWorkspaces/v3-trebuchet-release/AWSDotNetPublic/sdk/src/Core/Amazon.Runtime/Pipeline/Handlers/Signer.cs:38)
Amazon.Runtime.Internal.PipelineHandler.InvokeSync (IExecutionContext executionContext) (at E:/JenkinsWorkspaces/v3-trebuchet-release/AWSDotNetPublic/sdk/src/Core/Amazon.Runtime/Pipeline/PipelineHandler.cs:57)
Amazon.Runtime.Internal.CredentialsRetriever.InvokeSync (IExecutionContext executionContext) (at E:/JenkinsWorkspaces/v3-trebuchet-release/AWSDotNetPublic/sdk/src/Core/Amazon.Runtime/Pipeline/Handlers/CredentialsRetriever.cs:72)
Amazon.Runtime.Internal.PipelineHandler.InvokeSync (IExecutionContext executionContext) (at E:/JenkinsWorkspaces/v3-trebuchet-release/AWSDotNetPublic/sdk/src/Core/Amazon.Runtime/Pipeline/PipelineHandler.cs:57)
Amazon.Runtime.Internal.RetryHandler.InvokeSync (IExecutionContext executionContext) (at E:/JenkinsWorkspaces/v3-trebuchet-release/AWSDotNetPublic/sdk/src/Core/Amazon.Runtime/Pipeline/RetryHandler/RetryHandler.cs:74)
如果我想根据辅助索引查询，情况会变得更糟。为此，我需要在哈希和范围键之后附加一个dynamodboperationConfig：
var queryConfig = new DynamoDBOperationConfig() { IndexName = "PlayerIndex" };
AsyncSearch<POIVisit> query = AWSManager.Instance.DBContext.QueryAsync<POIVisit>(poiType, QueryOperator.Equal, PlayerID, queryConfig);
现在，似乎以某种方式认为，QueryConfig只是范围键的另一个值（因此，它基本上选择了QueryAsync的错误超载版本）。或者至少我认为发生了什么，因为我现在遇到了一个奇怪的转换错误：
InvalidCastException: Cannot cast from source type to destination type.
Amazon.DynamoDBv2.Converter`1[T].TryTo (System.Object value, Amazon.DynamoDBv2.DocumentModel.Primitive& p) (at E:/JenkinsWorkspaces/v3-trebuchet-release/AWSDotNetPublic/sdk/src/Services/DynamoDBv2/Custom/Conversion/DynamoDBEntryConversion.cs:630)
…
Amazon.DynamoDBv2.DataModel.DynamoDBContext.QueryAsync[POIVisit] (System.Object hashKeyValue, QueryOperator op, System.Object[] values) (at E:/JenkinsWorkspaces/v3-trebuchet-release/AWSDotNetPublic/sdk/src/Services/DynamoDBv2/Custom/DataModel/_unity/Context.Async.cs:550)
DBManager.RetrievePlayerVisits (System.String poiType, UnityEngine.Events.UnityAction`1 callback) (at Assets/Scripts/Managers/DBManager.cs:359)
我的Unity版本是5.6.3f1。我尝试了AWSSDK.DYNAMODBV2.3.3.4.18和较旧的AWSSDK.DYNAMODBV2.3.3.3.4.14 UNITY软件包，其中包含直接从Amazon下载的AWS SDK。
如果有人提示我做错了什么，我真的很感激，谢谢！
您需要在创建查询之前构建请求对象。我从来没有使用过统一性，但应该像
var request = new QueryRequest();
request.TableName = "YourTable";
request.KeyConditions = new Dictionary<string, Condition>()
{
{
"YourId", new Condition()
{
ComparisonOperator = "EQ",
AttributeValueList = new List<AttributeValue>()
{
new AttributeValue { S = YourId }
}
}
}
};
client.QueryAsync(request,(result));
具体来说，看来您没有将密钥调查作为请求的一部分，这是必需的。