英文:
RuntimeBinder exception when using System.Text.Json.Serialize with dynamic type
问题
在上述代码中运行后，我得到了以下输出（只在 Release 模式下，而不在 Debug 模式下！）
Microsoft.CSharp.RuntimeBinder.RuntimeBinderException: 调用在以下方法或属性之间模糊不清: 'System.Text.Json.JsonSerializer.Serialize<System.Text.Json.JsonSerializerOptions>(System.IO.Stream, System.Text.Json.JsonSerializerOptions, System.Text.Json.JsonSerializerOptions)' 和 'System.Text.Json.JsonSerializer.Serialize<System.Text.Json.JsonSerializerOptions>>(System.Text.Json.Utf8JsonWriter, System.Text.Json.JsonSerializerOptions, System.Text.Json.JsonSerializerOptions)' 在 CallSite.Target(Closure, CallSite, Type, Object, JsonSerializerOptions) 在 System.Dynamic.UpdateDelegates.UpdateAndExecute3[T0,T1,T2,TRet](CallSite site, T0 arg0, T1 arg1, T2 arg2) 在 Test.JsonUtil.PrettifyJson(String json) in D:\gitlab-runner\builds\RVQYCTWy\0\jpsc\developer\api-test\JsonUtil.cs:line 22
看起来存在一个问题，无法找到正确的 Serialize() 重载，因为第一个参数是 dynamic，但我不真的想在 PrettifyJson 上放置泛型类型，并且在 Debug 模式下它的工作正常。
有什么提示吗？
英文:
public string PrettifyJson(string json)
{
dynamic? parsedJson = JsonSerializer.Deserialize<dynamic>(json);
var optionPrettyPrint = new JsonSerializerOptions { WriteIndented = true };
string formattedJson = JsonSerializer.Serialize(parsedJson, optionPrettyPrint);
return formattedJson;
}
Running the above, I get (only in Release, not in Debug!)
> Microsoft.CSharp.RuntimeBinder.RuntimeBinderException: The call is ambiguous between the following methods or properties: 'System.Text.Json.JsonSerializer.Serialize<System.Text.Json.JsonSerializerOptions>(System.IO.Stream, System.Text.Json.JsonSerializerOptions, System.Text.Json.JsonSerializerOptions)' and 'System.Text.Json.JsonSerializer.Serialize<System.Text.Json.JsonSerializerOptions>(System.Text.Json.Utf8JsonWriter, System.Text.Json.JsonSerializerOptions, System.Text.Json.JsonSerializerOptions)' at CallSite.Target(Closure, CallSite, Type, Object, JsonSerializerOptions) at System.Dynamic.UpdateDelegates.UpdateAndExecute3[T0,T1,T2,TRet](CallSite site, T0 arg0, T1 arg1, T2 arg2) at Test.JsonUtil.PrettifyJson(String json) in D:\gitlab-runner\builds\RVQYCTWy\0\jpsc\developer\api-test\JsonUtil.cs:line 22
It seems there is a problem to find the correct Serialize() overload, since the first parameter is dynamic, but I don't really want to have to put a generic type on PrettifyJson, and it works as expected in Debug mode.
Any hints?
答案1
得分: 1
我可以重现这个问题：只需将"null"作为json的值传入。此时，parsedJson是一个空引用，并且有多个可适用的重载。
修复方法只是避免使用动态类型，就我所见，这里实际上并没有给你带来任何好处 - 只需使用object代替：
public string PrettifyJson(string json)
{
object? parsedJson = JsonSerializer.Deserialize<object>(json);
var optionPrettyPrint = new JsonSerializerOptions { WriteIndented = true };
string formattedJson = JsonSerializer.Serialize(parsedJson, optionPrettyPrint);
return formattedJson;
}
然后，当解析“null”时，仍然会调用JsonSerializer.Serialize<object>(null, optionPrettyPrint)，返回“null”。
英文:
I can reproduce the problem: just pass in "null" as the value for json. At that point, parsedJson is a null reference, and there are multiple overloads that are applicable.
The fix is to just avoid using dynamic typing, which isn't actually buying you anything here as far as I can see - just use object instead:
public string PrettifyJson(string json)
{
object? parsedJson = JsonSerializer.Deserialize<object>(json);
var optionPrettyPrint = new JsonSerializerOptions { WriteIndented = true };
string formattedJson = JsonSerializer.Serialize(parsedJson, optionPrettyPrint);
return formattedJson;
}
Then when "null" is parsed in, you still end up calling JsonSerializer.Serialize<object>(null, optionPrettyPrint) which returns "null" back.
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