在ASP.NET Core动作的响应中控制Guid格式

Question

Suppose my ASP.NET Core (API) action returns an object with this property:

[WhatGoesHere("N")]                  // ?
public Guid MyGuid { get; set; }

It will be serialized as ffd76e47-609f-42bc-b6b8-b66dedab5561 .

I want it to be serialized as ffd76e47609f42bcb6b8b66dedab5561 . In code that would be myGuid.ToString("N") .

Is there an attribute I can use to control the formatting?

Answer 1

You can implement a custom JsonConverter see here . And configure your aspnet core application to register this JsonConverter for output formatting. This way every time your application would serialize a Guid to JSON you'll get it the way you want it:

public void ConfigureServices(IServiceCollection services)
{
    services
        .AddMvc()
        .AddJsonOptions(options => {
            options.SerializerSettings.Converters.Add(new MyCustomConverter());
    });
}

You can also choose some particular classes to use the converter instead of all of them, by using this attribute on top of it:

[JsonConverter(typeof(MyCustomConverter))]
public class MyClass
{
    public Guid MyGuid { get;set; }
}

Answer 2

For a simple scenario like yours, the easiest way to do this is to have another property which formats the MyGuid by using MyGuid.ToString("N") . Where "N" means that you just need the digits without "-". Please see the documentation

You can add [JsonIgnore] to the MyGuid and add [JsonProperty("MyGuid")] attribute to the other property:

public class MyClass
{
    [JsonIgnore]
    public Guid MyGuid { get;set; }

    [JsonProperty("MyGuid")]
    public string DisplayGuid => MyGuid.ToString("N");
}

With the above in place, MyGuid property will be ignored. Instead, DisplayGuid property will be returned with the name MyGuid with the value ffd76e47609f42bcb6b8b66dedab5561

For more complex scenarios, you can surely go for a custom JsonConverter option as mentioned by @r1verside. I hope this helps

Answer 3

Based on @r1verside's answer, here is my implementation:

using System;

namespace MyProject {

  public sealed class GuidConverter : JsonConverter<Guid> {

    public GuidConverter() { }

    public GuidConverter(string format) { _format = format; }

    private readonly string _format = "N";

    public override void WriteJson(JsonWriter writer, Guid value, JsonSerializer serializer) {
      writer.WriteValue(value.ToString(_format));
    }

    public override Guid ReadJson(JsonReader reader, Type objectType, Guid existingValue, bool hasExistingValue, JsonSerializer serializer) {
      string s = (string)reader.Value;
      return new Guid(s);
    }

  }
}

It can be used like this:

[JsonConverter(typeof(GuidConverter))]    // defaults to format of "N"
public Guid MyGuid { get; set; }

but format can be overridden:

[JsonConverter(typeof(GuidConverter), "X")]
public Guid MyGuid { get; set; }