寻求同时兼容.NET Core与.NET 3.5的JSON序列化类库

Hey there, let's clear up some key misconceptions first—you’re working with outdated assumptions about these libraries, which is probably where the confusion is coming from!

First, the Facts About Library Support #

• Newtonsoft.Json (Json.NET) isn’t limited to .NET Framework. It’s fully cross-platform and supports .NET Core/.NET 5+ (and has for years). The latest stable versions work seamlessly across all modern .NET environments.
• System.Text.Json isn’t just for .NET Core either. While it’s built into .NET Core 3.0+ and .NET 5+, there’s an official NuGet package that lets you use it in .NET Framework 4.6.1 and later.

Why You’re Seeing Errors (and How to Fix Them) #

Most likely, your issues stem from incorrect package installation, misconfigured serialization code, or mismatched project target frameworks. Here’s a step-by-step fix:

1. Install the Right Packages Correctly

   • For Newtonsoft.Json:
     Use NuGet Package Manager to install the latest stable version, or run these commands:

     # Package Manager Console
     Install-Package Newtonsoft.Json
     
     # .NET CLI
     dotnet add package Newtonsoft.Json
     

     This works for both .NET Framework and .NET Core/.NET 5+.
   • For System.Text.Json:
     • .NET Core 3.0+/NET 5+: It’s included by default—no extra installation needed.
     • .NET Framework 4.6.1+: Install the official NuGet package System.Text.Json (stick to the latest compatible version for your framework).

2. Verify Your Serialization Code
   Double-check that you’re using the library’s APIs correctly. Here are basic examples:

   • Newtonsoft.Json:

     using Newtonsoft.Json;
     
     // Serialize
     string jsonOutput = JsonConvert.SerializeObject(yourObjectInstance);
     // Deserialize
     YourTargetType deserializedObj = JsonConvert.DeserializeObject<YourTargetType>(jsonOutput);
     

   • System.Text.Json:

     using System.Text.Json;
     
     // Serialize
     string jsonOutput = JsonSerializer.Serialize(yourObjectInstance);
     // Deserialize
     YourTargetType deserializedObj = JsonSerializer.Deserialize<YourTargetType>(jsonOutput);
     

   Note: If your class lacks a public parameterless constructor, System.Text.Json will throw an error by default. Fix this with configuration:

   var options = new JsonSerializerOptions
     {
         ConstructorHandling = JsonConstructorHandling.AllowNonPublicDefaultConstructor
         // Or for System.Text.Json:
         // ReferenceHandler = ReferenceHandler.IgnoreCycles (to fix loop references)
     };
     var deserializedObj = JsonSerializer.Deserialize<YourTargetType>(jsonOutput, options);
   

3. Fix Multi-Target Framework Conflicts
   If your project targets multiple frameworks (e.g., net472 and net6.0), ensure your package references are compatible across all targets. In your .csproj file, keep package references simple—most mainstream libraries auto-adapt:

   <ItemGroup>
     <PackageReference Include="Newtonsoft.Json" Version="13.0.3" />
   </ItemGroup>
   

4. Troubleshoot Common Errors

   • "Type cannot be serialized": Check that your class has public properties/fields, and resolve circular references (use [JsonIgnore] for Newtonsoft, or ReferenceHandler.IgnoreCycles for System.Text.Json).
   • Package version conflicts: Clear your NuGet cache, update all packages to their latest compatible versions, or add binding redirects in your .config file (for .NET Framework).

内容的提问来源于stack exchange，提问作者roozbeh S