反序列化 JSON 时，我收到 `System.InvalidCastException`

Question

So, basically, I have this simple JSON serializer/deserializer application in C# where I save StringCollections into .txt files that have JSON inside them. So, basically, I can successfully save my JSON to a raw text file like this:

String path = Properties.Settings.Default.database + "//data.txt";
StringCollection data = Properties.Settings.Default.data;

File.WriteAllText(path, JsonSerializer.Serialize(data));

But when desirializing the file to get the object using this code:

string rawJson = File.ReadAllText(path);
StringCollection data = JsonSerializer.Deserialize<StringCollection>(rawJson);

It gives me this exception:

System.InvalidCastException : 'Unable to cast object of type 'System.Text.Json.JsonElement' to type 'System.String'.'

I searched for this one StackOverflow and found a couple of posts about it, but they really didn't solve my problem. What am I doing wrong?

NOTE: I'm using System.Text.Json and not Newtonsoft.Json .

Answer 1

As Per Microsoft documentation the below is the supported types https://docs.microsoft.com/en-us/dotnet/standard/serialization/system-text-json-how-to :

.NET primitives that map to JavaScript primitives, such as numeric types, strings, and Boolean.
User-defined Plain Old CLR Objects (POCOs).
One-dimensional and jagged arrays (ArrayName[][]).
Dictionary<string,TValue> where TValue is object, JsonElement, or a POCO.
Collections from the following namespaces.
System.Collections
System.Collections.Generic
System.Collections.Immutable

So StringCollection is in System.Collections.Specialized namespace. So its not supported, you have 2 choices

1. Implement Custom Converter : https://docs.microsoft.com/en-us/dotnet/standard/serialization/system-text-json-converters-how-to
2. Change Your return type to for ex: List<string>