ASP.NET Core 修改/替換請求正文

Question

我想對HttpContext.Request.Body進行替換。

我試圖在中間件中做到這一點：

public async Task Invoke(HttpContext context)
{
    if (context.Request.Path.Value.Contains("DataSourceResult"))
    {
        var originalBody = new StreamReader(context.Request.Body).ReadToEnd();
        DataSourceRequest dataSource = null;

        try
        {
            dataSource = JsonConvert.DeserializeObject<DataSourceRequest>(originalBody);
        } catch
        {
            await _next.Invoke(context);
        }

        if (dataSource != null && dataSource.Take > 2000)
        {
            dataSource.Take = 2000;

            var bytesToWrite = dataSource.AsByteArray();
            await context.Request.Body.WriteAsync(bytesToWrite, 0, bytesToWrite.Length);
        }
        else
        {
            var bytesToWrite = originalBody.AsByteArray();
            await context.Request.Body.WriteAsync(bytesToWrite, 0, bytesToWrite.Length);
        }
    }

    await _next.Invoke(context);
}

第一個問題是body只能讀取一次，其次流是只讀的，不能寫入。

如何修改/替換Request.Body ？ 我需要更改請求正文的屬性值。

Answer 1

獲取請求正文，讀取其內容，進行任何必要的更改（如果有的話），然后創建一個新流以向下傳遞管道。 一旦訪問，請求流必須被替換。

public async Task Invoke(HttpContext context) {
    var request = context.Request;
    if (request.Path.Value.Contains("DataSourceResult")) {
        //get the request body and put it back for the downstream items to read
        var stream = request.Body;// currently holds the original stream                    
        var originalContent = new StreamReader(stream).ReadToEnd();
        var notModified = true;
        try {
            var dataSource = JsonConvert.DeserializeObject<DataSourceRequest>(originalContent);
            if (dataSource != null && dataSource.Take > 2000) {
                dataSource.Take = 2000;
                var json = JsonConvert.SerializeObject(dataSource);
                //replace request stream to downstream handlers
                var requestContent = new StringContent(json, Encoding.UTF8, "application/json");
                stream = await requestContent.ReadAsStreamAsync();//modified stream
                notModified = false;
            }
        } catch {
            //No-op or log error
        }
        if (notModified) {
            //put original data back for the downstream to read
            var requestData = Encoding.UTF8.GetBytes(originalContent);
            stream = new MemoryStream(requestData);
        }

        request.Body = stream;
    }
    await _next.Invoke(context);
}

Answer 2

就我而言，還需要將 Request.ContentLength 更新為新值。 我的解決方案是：

string originalContent;
using (StreamReader stream = new StreamReader(context.Request.Body))
{
    originalContent = stream.ReadToEnd();
}

var dataSource = JsonConvert.DeserializeObject<DataSourceRequest>(originalContent);
if (dataSource != null && dataSource.Take > 2000)
    dataSource.Take = 2000;

string json = JsonConvert.SerializeObject(dataSource);
var requestData = Encoding.UTF8.GetBytes(json);
context.Request.Body = new MemoryStream(requestData);
context.Request.ContentLength = context.Request.Body.Length;