public BoundRouteTemplate Bind(
            IDictionary <string, object> currentValues,
            IDictionary <string, object> values,
            HttpRouteValueDictionary defaultValues,
            HttpRouteValueDictionary constraints
            )
        {
            if (currentValues == null)
            {
                currentValues = new HttpRouteValueDictionary();
            }

            if (values == null)
            {
                values = new HttpRouteValueDictionary();
            }

            if (defaultValues == null)
            {
                defaultValues = new HttpRouteValueDictionary();
            }

            // The set of values we should be using when generating the URI in this route
            HttpRouteValueDictionary acceptedValues = new HttpRouteValueDictionary();

            // Keep track of which new values have been used
            HashSet <string> unusedNewValues = new HashSet <string>(
                values.Keys,
                StringComparer.OrdinalIgnoreCase
                );

            // Step 1: Get the list of values we're going to try to use to match and generate this URI

            // Find out which entries in the URI are valid for the URI we want to generate.
            // If the URI had ordered parameters a="1", b="2", c="3" and the new values
            // specified that b="9", then we need to invalidate everything after it. The new
            // values should then be a="1", b="9", c=<no value>.
            ForEachParameter(
                PathSegments,
                delegate(PathParameterSubsegment parameterSubsegment)
            {
                // If it's a parameter subsegment, examine the current value to see if it matches the new value
                string parameterName = parameterSubsegment.ParameterName;

                object newParameterValue;
                bool hasNewParameterValue = values.TryGetValue(
                    parameterName,
                    out newParameterValue
                    );
                if (hasNewParameterValue)
                {
                    unusedNewValues.Remove(parameterName);
                }

                object currentParameterValue;
                bool hasCurrentParameterValue = currentValues.TryGetValue(
                    parameterName,
                    out currentParameterValue
                    );

                if (hasNewParameterValue && hasCurrentParameterValue)
                {
                    if (!RoutePartsEqual(currentParameterValue, newParameterValue))
                    {
                        // Stop copying current values when we find one that doesn't match
                        return(false);
                    }
                }

                // If the parameter is a match, add it to the list of values we will use for URI generation
                if (hasNewParameterValue)
                {
                    if (IsRoutePartNonEmpty(newParameterValue))
                    {
                        acceptedValues.Add(parameterName, newParameterValue);
                    }
                }
                else
                {
                    if (hasCurrentParameterValue)
                    {
                        acceptedValues.Add(parameterName, currentParameterValue);
                    }
                }
                return(true);
            }
                );

            // Add all remaining new values to the list of values we will use for URI generation
            foreach (var newValue in values)
            {
                if (IsRoutePartNonEmpty(newValue.Value))
                {
                    if (!acceptedValues.ContainsKey(newValue.Key))
                    {
                        acceptedValues.Add(newValue.Key, newValue.Value);
                    }
                }
            }

            // Add all current values that aren't in the URI at all
            foreach (var currentValue in currentValues)
            {
                string parameterName = currentValue.Key;
                if (!acceptedValues.ContainsKey(parameterName))
                {
                    PathParameterSubsegment parameterSubsegment = GetParameterSubsegment(
                        PathSegments,
                        parameterName
                        );
                    if (parameterSubsegment == null)
                    {
                        acceptedValues.Add(parameterName, currentValue.Value);
                    }
                }
            }

            // Add all remaining default values from the route to the list of values we will use for URI generation
            ForEachParameter(
                PathSegments,
                delegate(PathParameterSubsegment parameterSubsegment)
            {
                if (!acceptedValues.ContainsKey(parameterSubsegment.ParameterName))
                {
                    object defaultValue;
                    if (
                        !IsParameterRequired(
                            parameterSubsegment,
                            defaultValues,
                            out defaultValue
                            )
                        )
                    {
                        // Add the default value only if there isn't already a new value for it and
                        // only if it actually has a default value, which we determine based on whether
                        // the parameter value is required.
                        acceptedValues.Add(parameterSubsegment.ParameterName, defaultValue);
                    }
                }
                return(true);
            }
                );

            // All required parameters in this URI must have values from somewhere (i.e. the accepted values)
            bool hasAllRequiredValues = ForEachParameter(
                PathSegments,
                delegate(PathParameterSubsegment parameterSubsegment)
            {
                object defaultValue;
                if (IsParameterRequired(parameterSubsegment, defaultValues, out defaultValue))
                {
                    if (!acceptedValues.ContainsKey(parameterSubsegment.ParameterName))
                    {
                        // If the route parameter value is required that means there's
                        // no default value, so if there wasn't a new value for it
                        // either, this route won't match.
                        return(false);
                    }
                }
                return(true);
            }
                );

            if (!hasAllRequiredValues)
            {
                return(null);
            }

            // All other default values must match if they are explicitly defined in the new values
            HttpRouteValueDictionary otherDefaultValues = new HttpRouteValueDictionary(
                defaultValues
                );

            ForEachParameter(
                PathSegments,
                delegate(PathParameterSubsegment parameterSubsegment)
            {
                otherDefaultValues.Remove(parameterSubsegment.ParameterName);
                return(true);
            }
                );

            foreach (var defaultValue in otherDefaultValues)
            {
                object value;
                if (values.TryGetValue(defaultValue.Key, out value))
                {
                    unusedNewValues.Remove(defaultValue.Key);
                    if (!RoutePartsEqual(value, defaultValue.Value))
                    {
                        // If there is a non-parameterized value in the route and there is a
                        // new value for it and it doesn't match, this route won't match.
                        return(null);
                    }
                }
            }

            // Step 2: If the route is a match generate the appropriate URI

            StringBuilder uri          = new StringBuilder();
            StringBuilder pendingParts = new StringBuilder();

            bool pendingPartsAreAllSafe = false;
            bool blockAllUriAppends     = false;

            for (int i = 0; i < PathSegments.Count; i++)
            {
                PathSegment pathSegment = PathSegments[i]; // parsedRouteUriPart

                if (pathSegment is PathSeparatorSegment)
                {
                    if (pendingPartsAreAllSafe)
                    {
                        // Accept
                        if (pendingParts.Length > 0)
                        {
                            if (blockAllUriAppends)
                            {
                                return(null);
                            }

                            // Append any pending literals to the URI
                            uri.Append(pendingParts.ToString());
                            pendingParts.Length = 0;
                        }
                    }
                    pendingPartsAreAllSafe = false;

                    // Guard against appending multiple separators for empty segments
                    if (pendingParts.Length > 0 && pendingParts[pendingParts.Length - 1] == '/')
                    {
                        // Dev10 676725: Route should not be matched if that causes mismatched tokens
                        // Dev11 86819: We will allow empty matches if all subsequent segments are null
                        if (blockAllUriAppends)
                        {
                            return(null);
                        }

                        // Append any pending literals to the URI (without the trailing slash) and prevent any future appends
                        uri.Append(pendingParts.ToString(0, pendingParts.Length - 1));
                        pendingParts.Length = 0;
                        blockAllUriAppends  = true;
                    }
                    else
                    {
                        pendingParts.Append("/");
                    }
                }
                else
                {
                    PathContentSegment contentPathSegment = pathSegment as PathContentSegment;
                    if (contentPathSegment != null)
                    {
                        // Segments are treated as all-or-none. We should never output a partial segment.
                        // If we add any subsegment of this segment to the generated URI, we have to add
                        // the complete match. For example, if the subsegment is "{p1}-{p2}.xml" and we
                        // used a value for {p1}, we have to output the entire segment up to the next "/".
                        // Otherwise we could end up with the partial segment "v1" instead of the entire
                        // segment "v1-v2.xml".
                        bool addedAnySubsegments = false;

                        for (int j = 0; j < contentPathSegment.Subsegments.Count; j++)
                        {
                            PathSubsegment        subsegment        = contentPathSegment.Subsegments[j];
                            PathLiteralSubsegment literalSubsegment =
                                subsegment as PathLiteralSubsegment;
                            if (literalSubsegment != null)
                            {
                                // If it's a literal we hold on to it until we are sure we need to add it
                                pendingPartsAreAllSafe = true;
                                pendingParts.Append(literalSubsegment.Literal);
                            }
                            else
                            {
                                PathParameterSubsegment parameterSubsegment =
                                    subsegment as PathParameterSubsegment;
                                if (parameterSubsegment != null)
                                {
                                    if (pendingPartsAreAllSafe)
                                    {
                                        // Accept
                                        if (pendingParts.Length > 0)
                                        {
                                            if (blockAllUriAppends)
                                            {
                                                return(null);
                                            }

                                            // Append any pending literals to the URI
                                            uri.Append(pendingParts.ToString());
                                            pendingParts.Length = 0;

                                            addedAnySubsegments = true;
                                        }
                                    }
                                    pendingPartsAreAllSafe = false;

                                    // If it's a parameter, get its value
                                    object acceptedParameterValue;
                                    bool   hasAcceptedParameterValue = acceptedValues.TryGetValue(
                                        parameterSubsegment.ParameterName,
                                        out acceptedParameterValue
                                        );
                                    if (hasAcceptedParameterValue)
                                    {
                                        unusedNewValues.Remove(parameterSubsegment.ParameterName);
                                    }

                                    object defaultParameterValue;
                                    defaultValues.TryGetValue(
                                        parameterSubsegment.ParameterName,
                                        out defaultParameterValue
                                        );

                                    if (
                                        RoutePartsEqual(
                                            acceptedParameterValue,
                                            defaultParameterValue
                                            )
                                        )
                                    {
                                        // If the accepted value is the same as the default value, mark it as pending since
                                        // we won't necessarily add it to the URI we generate.
                                        pendingParts.Append(
                                            Convert.ToString(
                                                acceptedParameterValue,
                                                CultureInfo.InvariantCulture
                                                )
                                            );
                                    }
                                    else
                                    {
                                        if (blockAllUriAppends)
                                        {
                                            return(null);
                                        }

                                        // Add the new part to the URI as well as any pending parts
                                        if (pendingParts.Length > 0)
                                        {
                                            // Append any pending literals to the URI
                                            uri.Append(pendingParts.ToString());
                                            pendingParts.Length = 0;
                                        }
                                        uri.Append(
                                            Convert.ToString(
                                                acceptedParameterValue,
                                                CultureInfo.InvariantCulture
                                                )
                                            );

                                        addedAnySubsegments = true;
                                    }
                                }
                                else
                                {
                                    Contract.Assert(false, "Invalid path subsegment type");
                                }
                            }
                        }

                        if (addedAnySubsegments)
                        {
                            // See comment above about why we add the pending parts
                            if (pendingParts.Length > 0)
                            {
                                if (blockAllUriAppends)
                                {
                                    return(null);
                                }

                                // Append any pending literals to the URI
                                uri.Append(pendingParts.ToString());
                                pendingParts.Length = 0;
                            }
                        }
                    }
                    else
                    {
                        Contract.Assert(false, "Invalid path segment type");
                    }
                }
            }

            if (pendingPartsAreAllSafe)
            {
                // Accept
                if (pendingParts.Length > 0)
                {
                    if (blockAllUriAppends)
                    {
                        return(null);
                    }

                    // Append any pending literals to the URI
                    uri.Append(pendingParts.ToString());
                }
            }

            // Process constraints keys
            if (constraints != null)
            {
                // If there are any constraints, mark all the keys as being used so that we don't
                // generate query string items for custom constraints that don't appear as parameters
                // in the URI format.
                foreach (var constraintsItem in constraints)
                {
                    unusedNewValues.Remove(constraintsItem.Key);
                }
            }

            // Encode the URI before we append the query string, otherwise we would double encode the query string
            StringBuilder encodedUri = new StringBuilder();

            encodedUri.Append(UriEncode(uri.ToString()));
            uri = encodedUri;

            // Add remaining new values as query string parameters to the URI
            if (unusedNewValues.Count > 0)
            {
                // Generate the query string
                bool firstParam = true;
                foreach (string unusedNewValue in unusedNewValues)
                {
                    object value;
                    if (acceptedValues.TryGetValue(unusedNewValue, out value))
                    {
                        uri.Append(firstParam ? '?' : '&');
                        firstParam = false;
                        uri.Append(Uri.EscapeDataString(unusedNewValue));
                        uri.Append('=');
                        uri.Append(
                            Uri.EscapeDataString(
                                Convert.ToString(value, CultureInfo.InvariantCulture)
                                )
                            );
                    }
                }
            }

            return(new BoundRouteTemplate
            {
                BoundTemplate = uri.ToString(),
                Values = acceptedValues
            });
        }