问请问Tencent Cos 预签名url，支持post方法吗？

            PreSignatureStruct preSignatureStruct = new PreSignatureStruct()
            {
                appid = _tencentCosConfig.AppId,
                region = _tencentCosConfig.Region,
                bucket = _tencentCosConfig.BucketName,
                key = tencentId,
                httpMethod = "POST",
                isHttps = true,
                signDurationSecond = durationSeconds,
                headers = null,
                queryParameters = null
            };

<?xml version='1.0' encoding='utf-8' ?>
<Error>
    <Code>MalformedPOSTRequest</Code>
    <Message>The body of your POST request is not well-formed multipart/form-data.</Message>
    <Resource>media-hub-cn-staging-1258166938.cos.ap-shanghai.myqcloud.com/a60d0c3b-fb96-4df2-acb8-6c1aae3e598a.jpg</Resource>
    <RequestId>NWRiYmQ5MzhfNzEyZjIyMDlfZGE4OF84Njk5NjM=</RequestId>
    <TraceId>OGVmYzZiMmQzYjA2OWNhODk0NTRkMTBiOWVmMDAxODc0OWRkZjk0ZDM1NmI1M2E2MTRlY2MzZDhmNmI5MWI1OTczMmZiNDZmZjBmNTVjMGU4NTViNDhhYWVjNzNkNzI4MzIyMTZjZTI0YWNhOTM4ZDlhNGM3NDA5MDQ1NjE3NTM=</TraceId>
</Error>