可以使用BizTalk的自定义pipeline组件来解决这个问题。

首先，创建一个新的C#类库项目。然后，添加Microsoft.BizTalk.Pipeline.dll引用。

接下来，创建一个自定义pipeline组件类并继承自JsonEncoder。重写Encode方法，将null-boolean值转换为null字符串值。

示例代码如下：

using System.IO; using System.Text; using Microsoft.BizTalk.Component.Interop; using Microsoft.BizTalk.Message.Interop; using Microsoft.BizTalk.Streaming; using Newtonsoft.Json;

namespace MyBizTalkPipelineComponents { [ComponentCategory(CategoryTypes.CATID_PipelineComponent)] [System.Runtime.InteropServices.Guid("230B7FBB-CAD4-4DC8-82D1-2DFC29179402")] [ComponentCategory(CategoryTypes.CATID_Encoder)] public class MyJsonEncoder : JsonEncoder { public override IBaseMessage Encode(IPipelineContext pc, IBaseMessage inmsg) { var encoding = new UTF8Encoding(false); var buffer = new MemoryStream(); var jsonWriter = new JsonTextWriter(new StreamWriter(new IgnoreBomStream(buffer), encoding)); var messageStream = inmsg.BodyPart.GetOriginalDataStream(); var reader = new StreamReader(messageStream, encoding); var messageBody = reader.ReadToEnd(); var messageObject = JsonConvert.DeserializeObject(messageBody); messageObject = ConvertNullBooleansToNullStrings(messageObject);

        var serializer = new JsonSerializer();
        serializer.NullValueHandling = NullValueHandling.Ignore;
        serializer.Formatting = Formatting.None;
        serializer.Serialize(jsonWriter, messageObject);

        var outputMessage = inmsg;
        var outputBodyPart = outputMessage.BodyPart;

        outputBodyPart.Data = new ReadOnlySeekableStream(buffer);
        outputMessage.BodyPart = outputBodyPart;

        return outputMessage;
    }

    private object ConvertNullBooleansToNullStrings(object messageObject)
    {
        if (messageObject is JObject jobj)
        {
            foreach (var prop in jobj.Properties())
            {
                if (prop.Value.Type == JTokenType.Null && prop.Value.Parent is JProperty parent)
                {
                    parent.Value = JValue.CreateString((string)null);
                }
                else