Amazon.S3.AmazonS3Client.CreateSignedPolicy C# (CSharp) Method

        private void CreateSignedPolicy(PostObjectRequest request)
        {
            StringBuilder metadataPolicy = new StringBuilder();
            foreach (var kvp in request.Metadata)
            {
                var metakey = kvp.Key.StartsWith(S3Constants.PostFormDataXAmzPrefix, StringComparison.Ordinal) ? kvp.Key : S3Constants.PostFormDataMetaPrefix + kvp.Key;
                metadataPolicy.Append(string.Format(",{{\"{0}\": \"{1}\"}}", metakey, kvp.Value));
            }

            StringBuilder headersPolicy = new StringBuilder();
            foreach (var key in request.Headers.Keys)
            {
                headersPolicy.Append(string.Format(",{{\"{0}\": \"{1}\"}}", key, request.Headers[key]));
            }

            string policyString = null;
            int position = request.Key.LastIndexOf('/');
            if (position == -1)
            {
                policyString = "{\"expiration\": \"" + DateTime.UtcNow.AddHours(24).ToString("yyyy-MM-ddTHH:mm:ssZ") + "\",\"conditions\": [{\"bucket\": \"" +
                    request.Bucket + "\"},[\"starts-with\", \"$key\", \"" + "\"],{\"acl\": \"" + request.CannedACL.Value + "\"},[\"eq\", \"$Content-Type\", " +
                    "\"" + request.Headers.ContentType + "\"" + "]" + metadataPolicy.ToString() + headersPolicy.ToString() + "]}";
            }
            else
            {
                policyString = "{\"expiration\": \"" + DateTime.UtcNow.AddHours(24).ToString("yyyy-MM-ddTHH:mm:ssZ") + "\",\"conditions\": [{\"bucket\": \"" +
                    request.Bucket + "\"},[\"starts-with\", \"$key\", \"" + request.Key.Substring(0, position) + "/\"],{\"acl\": \"" + request.CannedACL.Value +
                    "\"},[\"eq\", \"$Content-Type\", " + "\"" + request.Headers.ContentType + "\"" + "]" + metadataPolicy.ToString() + headersPolicy.ToString() + "]}";
            }
            if (Config.SignatureVersion == "2")
            {
                request.SignedPolicy = S3PostUploadSignedPolicy.GetSignedPolicy(policyString, base.Credentials);
            }
            else
            {
                request.SignedPolicy = S3PostUploadSignedPolicy.GetSignedPolicyV4(policyString, base.Credentials, request.Region);
            }
        }