ASP.NET Core Web API无法显示DataTable的问题求助

代码示例 #

控制器代码 #

[Route("api/[controller]")]
[ApiController]
public class MapDataTableDemo : ControllerBase
{
    Product p;
    
    public MapDataTableDemo()
    {
        p = new Product();
    }
     
    [HttpGet]
    public async Task<IActionResult> MapDataTable()
    {
        var response = p.GetDataTable();
        return Ok(response);
    }
}

Product模型类代码 #

public class Product
{
    public DataTable dataTable { get; set; }

    public DataTable GetDataTable()
    {
        this.dataTable = new DataTable();
        this.dataTable.Columns.Add("product name");
        this.dataTable.Columns.Add("product price");
        this.dataTable.Rows.Add("mobile", 20000);
        this.dataTable.Rows.Add("tv", 15000);
        this.dataTable.Rows.Add("washing machine", 30000);
        return this.dataTable;
    }
}

报错信息 #

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)

at System.Text.Json.Serialization.JsonConverter1.TryWrite(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state) at System.Text.Json.Serialization.JsonConverter1.TryWriteAsObject(Utf8JsonWriter writer, Object value, JsonSerializerOptions options, WriteStack& state)

at System.Text.Json.Serialization.JsonConverter1.TryWrite(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state) at System.Text.Json.Serialization.Converters.IEnumerableConverter1.OnWriteResume(Utf8JsonWriter writer, TCollection value, JsonSerializerOptions options, WriteStack& state)

at System.Text.Json.Serialization.JsonCollectionConverter`2.OnTryWrite(Utf8JsonWriter writer, TCollection value, JsonSerializerOptions options, WriteStack& state)

解决办法 #

方法1：将DataTable转换为匿名对象列表（推荐） #

直接把DataTable的行数据转换成前端易处理的匿名对象集合，避开DataTable本身的复杂结构：

[HttpGet]
public IActionResult MapDataTable()
{
    var dt = p.GetDataTable();
    var result = dt.AsEnumerable()
                   .Select(row => new
                   {
                       ProductName = row["product name"].ToString(),
                       ProductPrice = Convert.ToDecimal(row["product price"])
                   })
                   .ToList();
    return Ok(result);
}

方法2：自定义Json转换器处理DataTable #

创建转换器只序列化行数据和列名，忽略无法序列化的属性：

1. 定义转换器类：

public class DataTableConverter : JsonConverter<DataTable>
{
    public override DataTable Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
    {
        throw new NotImplementedException(); // 无需反序列化可留空
    }

    public override void Write(Utf8JsonWriter writer, DataTable value, JsonSerializerOptions options)
    {
        writer.WriteStartArray();
        foreach (DataRow row in value.Rows)
        {
            writer.WriteStartObject();
            foreach (DataColumn col in value.Columns)
            {
                writer.WritePropertyName(col.ColumnName);
                JsonSerializer.Serialize(writer, row[col], options);
            }
            writer.WriteEndObject();
        }
        writer.WriteEndArray();
    }
}

2. 在Program.cs注册转换器：

builder.Services.AddControllers()
    .AddJsonOptions(options =>
    {
        options.JsonSerializerOptions.Converters.Add(new DataTableConverter());
    });

方法3：改用Newtonsoft.Json替代System.Text.Json #

Newtonsoft.Json对DataTable序列化支持更完善：

1. 安装NuGet包：Microsoft.AspNetCore.Mvc.NewtonsoftJson
2. 在Program.cs配置：

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

配置完成后原代码可直接返回DataTable。

内容的提问来源于stack exchange，提问作者Aman