HttpRequest和POST

Question

我一直收到以下错误消息之一：

"The remote server returned an error: (400) Bad Request."  
               OR
"System.Net.ProtocolViolationException: You must write ContentLength bytes to the request stream before calling [Begin]GetResponse."

下面是我正在运行的代码：

        StringBuilder bld = new StringBuilder();
        bld.Append("contractId=");
        bld.Append(ctrId);
        bld.Append("&companyIds=");
        bld.Append("'" + company1+ ", " + company2+ "'");

        HttpWebRequest req = (HttpWebRequest)WebRequest
            .Create(secureServiceUrl + "SetContractCompanyLinks");
        req.Credentials = service.Credentials;
        //req.AllowWriteStreamBuffering = true;
        req.Method = "POST";
        req.ContentType = "application/x-www-form-urlencoded";
        req.ContentLength = bld.Length;
        StreamWriter writer = new StreamWriter(req.GetRequestStream());
        var encodedData = Encoding.ASCII.GetBytes(bld.ToString());
        writer.Write(encodedData);
        writer.Flush();
        writer.Close();
        var resp = req.GetResponse();

Answer 1

有几件事是“关”的：

直接写到你的写入器，不应该有理由调用GetBytes()。StreamWriter完全能够将字符串写入到流中：

writer.Write(bld.ToString());

在StreamWriter周围使用() {}模式

这将确保正确处理编写器对象。

using(var writer = new StreamWriter(req.GetRequestStream()))
{
   writer.Write(bld.ToString());
}

你不需要显式地设置内容长度别管它，框架会根据你写到请求流中的内容来设置它。

如果需要明确说明如何使用ASCII码，请在Content-Type头中设置字符集

req.ContentType = "application/x-www-form-urlencoded; charset=ASCII";

您还应该在实例化StreamWriter时指定编码：

new StreamWriter(req.GetRequestStream(), Encoding.ASCII)

Answer 2

    req.ContentLength = bld.Length;
    StreamWriter writer = new StreamWriter(req.GetRequestStream());
    var encodedData = Encoding.ASCII.GetBytes(bld.ToString());
    writer.Write(encodedData);

你写的不是你说要写的东西--你写的是ASCII编码的字节，而不是原始的字节数组-- ContentLength必须与你写的字节数相匹配。取而代之的是：

    var encodedData = Encoding.ASCII.GetBytes(bld.ToString());
    req.ContentLength = encodedData.Length;