c# - ASP.NET Core 修改/替换请求体

Question

我想对 HttpContext.Request.Body 进行替换。

我尝试在中间件中完成:

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);
}

第一个问题是body只能读一次，其次流是只读的，不能写。

如何修改/替换 Request.Body？我需要更改请求正文的属性值。

Answer 1

获取请求正文，读取其内容，进行任何必要的更改(如果有的话)，然后创建一个新流以向下传递管道。一旦访问，就必须替换请求流。

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);
}