System.NotSupportedException: Serialization and deserialization of 'System.Type' instances are not supported. Path: $.Columns.DataType.

Question

On my Asp.net core web api application, I'm query the database using ADO.Net and want to return the data table to the client, but it will show the 500 error with the following error message:

System.NotSupportedException: Serialization and deserialization of 'System.Type' instances are not supported. Path: $.Columns.DataType. System.NotSupportedException: Serialization and deserialization of 'System.Type' instances are not supported. at System.Text.Json.Serialization.Converters.UnsupportedTypeConverter1.Write(Utf8JsonWriter writer, T value, JsonSerializerOptions options) at System.Text.Json.Serialization.JsonConverter1.TryWrite(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)at System.Text.Json.Serialization.Metadata.JsonPropertyInfo1.GetMemberAndWriteJson(Object obj, WriteStack& state, Utf8JsonWriter writer) at System.Text.Json.Serialization.Converters.ObjectDefaultConverter1.OnTryWrite(Utf8JsonWriter writer, T value, JsonSerializerOptions options, WriteStack& state)

Can someone help me solve this problem? Thx.

Answer 1

Hi @Jim Olewis

From the official document, we can see that the System.Text.Json doesn't provide built-in support for the DataTable and related types.

So, you can try to use NewtonsoftJson package to serialization the data table in asp.net core application.

Try to install the Microsoft.AspNetCore.Mvc.NewtonsoftJson via the NuGet package.

Then, register the AddNewtonsoftJson() method in the program.cs file:

builder.Services.AddControllers().AddNewtonsoftJson();

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