Convert concatenation string to interpolation for System.Private.Xml

src/libraries/System.Private.Xml/src/System/Xml/BinaryXml/XmlBinaryReader.cs

@@ -120,7 +120,7 @@ public override string ToString()
                 if (prefix.Length == 0)
                     return this.localname;
                 else
-                    return this.prefix + ":" + this.localname;
+                    return $"{this.prefix}:{this.localname}";
             }
 
             public static bool operator ==(QName a, QName b)
@@ -4048,7 +4048,7 @@ private string ValueAsString(BinXmlToken token)
                             if (qname.prefix.Length == 0)
                                 return qname.localname;
                             else
-                                return string.Concat(qname.prefix, ":", qname.localname);
+                                return $"{qname.prefix}:{qname.localname}";
                         }
 
                     default:
@@ -4422,7 +4422,7 @@ private object ValueAs(BinXmlToken token, Type returnType, IXmlNamespaceResolver
 
         private Exception ThrowUnexpectedToken(BinXmlToken token)
         {
-            System.Diagnostics.Debug.WriteLine("Unhandled token: " + token.ToString());
+            System.Diagnostics.Debug.WriteLine($"Unhandled token: {token}");
             return ThrowXmlException(SR.XmlBinary_UnexpectedToken);
         }
 

src/libraries/System.Private.Xml/src/System/Xml/Cache/XPathNode.cs

@@ -97,7 +97,7 @@ public string Name
                 }
                 else
                 {
-                    return string.Concat(Prefix, ":", LocalName);
+                    return $"{Prefix}:{LocalName}";
                 }
             }
         }

src/libraries/System.Private.Xml/src/System/Xml/Core/QueryOutputWriter.cs

@@ -163,7 +163,7 @@ public override void WriteStartElement(string? prefix, string localName, string?
             if (_outputDocType)
             {
                 _wrapped.WriteDocType(
-                        string.IsNullOrEmpty(prefix) ? localName : prefix + ":" + localName,
+                        string.IsNullOrEmpty(prefix) ? localName : $"{prefix}:{localName}",
                         _publicId,
                         _systemId,
                         null);

src/libraries/System.Private.Xml/src/System/Xml/Core/QueryOutputWriterV1.cs

@@ -145,7 +145,7 @@ public override void WriteStartElement(string? prefix, string localName, string?
                 if (ws == WriteState.Start || ws == WriteState.Prolog)
                 {
                     _wrapped.WriteDocType(
-                            string.IsNullOrEmpty(prefix) ? localName : prefix + ":" + localName,
+                            string.IsNullOrEmpty(prefix) ? localName : $"{prefix}:{localName}",
                             _publicId,
                             _systemId,
                             null);

src/libraries/System.Private.Xml/src/System/Xml/Core/ValidatingReaderNodeData.cs

@@ -84,7 +84,7 @@ public string GetAtomizedNameWPrefix(XmlNameTable nameTable)
                 }
                 else
                 {
-                    _nameWPrefix = nameTable.Add(string.Concat(_prefix, ":", _localName));
+                    _nameWPrefix = nameTable.Add($"{_prefix}:{_localName}");
                 }
             }
 

src/libraries/System.Private.Xml/src/System/Xml/Core/XmlEventCache.cs

@@ -242,7 +242,7 @@ public void EventsToWriter(XmlWriter writer)
                             break;
 
                         default:
-                            Debug.Fail("Unknown event: " + page[idxEvent].EventType);
+                            Debug.Fail($"Unknown event: {page[idxEvent].EventType}");
                             break;
                     }
                 }

src/libraries/System.Private.Xml/src/System/Xml/Core/XmlSubtreeReader.cs

@@ -1326,7 +1326,7 @@ private void AddNamespace(string prefix, string ns)
             {
                 localName = prefix;
                 attrPrefix = _xmlns;
-                name = reader.NameTable.Add(string.Concat(_xmlns, ":", prefix));
+                name = reader.NameTable.Add($"{_xmlns}:{prefix}");
             }
 
             if (_nsAttributes[index] == null)

src/libraries/System.Private.Xml/src/System/Xml/Core/XmlTextReaderImpl.cs

@@ -555,7 +555,7 @@ internal XmlTextReaderImpl(string xmlFragment, XmlNodeType fragType, XmlParserCo
         internal XmlTextReaderImpl(string xmlFragment, XmlParserContext? context)
             : this(null == context || null == context.NameTable ? new NameTable() : context.NameTable)
         {
-            InitStringInput((context == null) ? string.Empty : context.BaseURI, Encoding.Unicode, string.Concat("<?xml ", xmlFragment, "?>"));
+            InitStringInput((context == null) ? string.Empty : context.BaseURI, Encoding.Unicode, $"<?xml {xmlFragment}?>");
             InitFragmentReader(XmlNodeType.XmlDeclaration, context, true);
         }
 

src/libraries/System.Private.Xml/src/System/Xml/Core/XmlTextReaderImplHelpers.cs

@@ -681,7 +681,7 @@ internal string CreateNameWPrefix(XmlNameTable nt)
                 }
                 else
                 {
-                    nameWPrefix = nt.Add(string.Concat(prefix, ":", localName));
+                    nameWPrefix = nt.Add($"{prefix}:{localName}");
                 }
                 return nameWPrefix;
             }

src/libraries/System.Private.Xml/src/System/Xml/Core/XmlTextWriter.cs

@@ -450,15 +450,15 @@ public override void WriteDocType(string name, string? pubid, string? sysid, str
                 _textWriter.Write(name);
                 if (pubid != null)
                 {
-                    _textWriter.Write(" PUBLIC " + _quoteChar);
+                    _textWriter.Write($" PUBLIC {_quoteChar}");
                     _textWriter.Write(pubid);
-                    _textWriter.Write(_quoteChar + " " + _quoteChar);
+                    _textWriter.Write($"{_quoteChar} {_quoteChar}");
                     _textWriter.Write(sysid);
                     _textWriter.Write(_quoteChar);
                 }
                 else if (sysid != null)
                 {
-                    _textWriter.Write(" SYSTEM " + _quoteChar);
+                    _textWriter.Write($" SYSTEM {_quoteChar}");
                     _textWriter.Write(sysid);
                     _textWriter.Write(_quoteChar);
                 }
@@ -1592,8 +1592,7 @@ private void PopNamespaces(int indexFrom, int indexTo)
         private string GeneratePrefix()
         {
             int temp = _stack[_top].prefixCount++ + 1;
-            return "d" + _top.ToString("d", CultureInfo.InvariantCulture)
-                + "p" + temp.ToString("d", CultureInfo.InvariantCulture);
+            return string.Create(CultureInfo.InvariantCulture, $"d{_top:d}p{temp:d}");
         }
 
         private void InternalWriteProcessingInstruction(string name, string? text)

src/libraries/System.Private.Xml/src/System/Xml/Core/XmlWellFormedWriter.cs

@@ -2074,7 +2074,7 @@ private static string GetStateName(State state)
         {
             if (state >= State.Error)
             {
-                Debug.Fail("We should never get to this point. State = " + state);
+                Debug.Fail($"We should never get to this point. State = {state}");
                 return "Error";
             }
             else
@@ -2176,7 +2176,7 @@ private void ThrowInvalidStateTransition(Token token, State currentState)
                 case State.Start:
                     if (_conformanceLevel == ConformanceLevel.Document)
                     {
-                        throw new InvalidOperationException(wrongTokenMessage + ' ' + SR.Xml_ConformanceLevelFragment);
+                        throw new InvalidOperationException($"{wrongTokenMessage} {SR.Xml_ConformanceLevelFragment}");
                     }
                     break;
             }

src/libraries/System.Private.Xml/src/System/Xml/Core/XsdValidatingReader.cs

@@ -244,7 +244,7 @@ public override string Name
                     string? prefix = _validator.GetDefaultAttributePrefix(_cachedNode.Namespace);
                     if (prefix != null && prefix.Length != 0)
                     {
-                        return prefix + ":" + _cachedNode.LocalName;
+                        return $"{prefix}:{_cachedNode.LocalName}";
                     }
 
                     return _cachedNode.LocalName;

src/libraries/System.Private.Xml/src/System/Xml/Dom/DocumentXmlWriter.cs

@@ -441,7 +441,7 @@ private void CloseWithAppendAttribute()
                 if (offset != -1
                     && ((XmlAttribute)attrs.nodes[offset]).Specified)
                 {
-                    throw new XmlException(SR.Xml_DupAttributeName, attr.Prefix.Length == 0 ? attr.LocalName : string.Concat(attr.Prefix, ":", attr.LocalName));
+                    throw new XmlException(SR.Xml_DupAttributeName, attr.Prefix.Length == 0 ? attr.LocalName : $"{attr.Prefix}:{attr.LocalName}");
                 }
             }
             for (int i = 0; i < _fragment.Count; i++)

src/libraries/System.Private.Xml/src/System/Xml/Dom/XmlEntityReference.cs

@@ -188,7 +188,7 @@ private string ConstructBaseURI(string baseURI, string systemId)
             if (nCount > 0 && nCount < baseURI.Length)
                 buf = baseURI.Substring(0, nCount);
             else if (nCount == 0)
-                buf = buf + "\\";
+                buf = $"{buf}\\";
             return (buf + systemId.Replace('\\', '/'));
         }
 

src/libraries/System.Private.Xml/src/System/Xml/Dom/XmlLoader.cs

@@ -865,7 +865,7 @@ private void RemoveDuplicateNamespace(XmlElement elem, XmlNamespaceManager mgr,
 
         private string EntitizeName(string name)
         {
-            return "&" + name + ";";
+            return $"&{name};";
         }
 
         //The function is called when expanding the entity when its children being asked

src/libraries/System.Private.Xml/src/System/Xml/Dom/XmlName.cs

@@ -91,7 +91,7 @@ public string Name
                     {
                         if (_localName.Length > 0)
                         {
-                            string n = string.Concat(_prefix, ":", _localName);
+                            string n = $"{_prefix}:{_localName}";
                             lock (ownerDoc.NameTable)
                             {
                                 if (_name == null)

src/libraries/System.Private.Xml/src/System/Xml/Dom/XmlNode.cs

@@ -1471,23 +1471,23 @@ public override string ToString()
                 {
                     case XmlNodeType.Element:
                     case XmlNodeType.EntityReference:
-                        result += ", Name=\"" + _node.Name + "\"";
+                        result += $", Name=\"{_node.Name}\"";
                         break;
                     case XmlNodeType.Attribute:
                     case XmlNodeType.ProcessingInstruction:
-                        result += ", Name=\"" + _node.Name + "\", Value=\"" + XmlConvert.EscapeValueForDebuggerDisplay(_node.Value!) + "\"";
+                        result += $", Name=\"{_node.Name}\", Value=\"{XmlConvert.EscapeValueForDebuggerDisplay(_node.Value!)}\"";
                         break;
                     case XmlNodeType.Text:
                     case XmlNodeType.CDATA:
                     case XmlNodeType.Comment:
                     case XmlNodeType.Whitespace:
                     case XmlNodeType.SignificantWhitespace:
                     case XmlNodeType.XmlDeclaration:
-                        result += ", Value=\"" + XmlConvert.EscapeValueForDebuggerDisplay(_node.Value!) + "\"";
+                        result += $", Value=\"{XmlConvert.EscapeValueForDebuggerDisplay(_node.Value!)}\"";
                         break;
                     case XmlNodeType.DocumentType:
                         XmlDocumentType documentType = (XmlDocumentType)_node;
-                        result += ", Name=\"" + documentType.Name + "\", SYSTEM=\"" + documentType.SystemId + "\", PUBLIC=\"" + documentType.PublicId + "\", Value=\"" + XmlConvert.EscapeValueForDebuggerDisplay(documentType.InternalSubset!) + "\"";
+                        result += $", Name=\"{documentType.Name}\", SYSTEM=\"{documentType.SystemId}\", PUBLIC=\"{documentType.PublicId}\", Value=\"{XmlConvert.EscapeValueForDebuggerDisplay(documentType.InternalSubset!)}\"";
                         break;
                     default:
                         break;

src/libraries/System.Private.Xml/src/System/Xml/Dom/XmlNodeReader.cs

@@ -247,7 +247,7 @@ public string Value
                         InitDecAttr();
                     for (int i = 0; i < _nDeclarationAttrCount; i++)
                     {
-                        strb.Append(decNodeAttributes[i].name + "=\"" + decNodeAttributes[i].value + "\"");
+                        strb.Append($"{decNodeAttributes[i].name}=\"{decNodeAttributes[i].value}\"");
                         if (i != (_nDeclarationAttrCount - 1))
                             strb.Append(' ');
                     }
@@ -859,7 +859,7 @@ public bool MoveToElement()
             if (prefix.Length == 0)
                 attrName = "xmlns";
             else
-                attrName = "xmlns:" + prefix;
+                attrName = $"xmlns:{prefix}";
 
             // walk up the XmlNode parent chain, looking for the xmlns attribute
             XmlNode? node = _curNode;

src/libraries/System.Private.Xml/src/System/Xml/Schema/ContentValidator.cs

@@ -233,7 +233,7 @@ public string NameOf(int symbol)
                 {
                     if ((int)de!.Value! == symbol)
                     {
-                        return (string)de.Key + ":*";
+                        return $"{(string)de.Key}:*";
                     }
                 }
             }

src/libraries/System.Private.Xml/src/System/Xml/Schema/XdrBuilder.cs

@@ -653,7 +653,7 @@ private static void XDR_BeginRoot(XdrBuilder builder)
             { // inline xdr schema
                 if (builder._XdrName != null)
                 {
-                    builder._TargetNamespace = builder._NameTable.Add("x-schema:#" + builder._XdrName);
+                    builder._TargetNamespace = builder._NameTable.Add($"x-schema:#{builder._XdrName}");
                 }
                 else
                 {

src/libraries/System.Private.Xml/src/System/Xml/Schema/XmlSchemaAny.cs

@@ -69,7 +69,7 @@ internal override string NameString
                         int i = 1;
                         foreach (string wildcardNS in _namespaceList.Enumerate)
                         {
-                            sb.Append(wildcardNS + ":*");
+                            sb.Append($"{wildcardNS}:*");
                             if (i < _namespaceList.Enumerate.Count)
                             {
                                 sb.Append(' ');

src/libraries/System.Private.Xml/src/System/Xml/Schema/XmlSchemaDataType.cs

@@ -106,7 +106,7 @@ internal string TypeCodeString
                         }
                         else
                         {
-                            typeCodeString = "List of " + TypeCodeToString(typeCode);
+                            typeCodeString = $"List of {TypeCodeToString(typeCode)}";
                         }
                         break;
 

src/libraries/System.Private.Xml/src/System/Xml/Schema/XmlSchemaException.cs

@@ -145,7 +145,7 @@ internal XmlSchemaException(string? res, string?[]? args, Exception? innerExcept
             }
             catch (MissingManifestResourceException)
             {
-                return "UNKNOWN(" + res + ")";
+                return $"UNKNOWN({res})";
             }
         }
 

src/libraries/System.Private.Xml/src/System/Xml/Schema/XmlSchemaValidator.cs

@@ -2304,7 +2304,7 @@ private void ElementIdentityConstraints()
                     {
                         // selector selects new node, activate a new set of fields
                         Debug.WriteLine("Selector Match!");
-                        Debug.WriteLine("Name: " + localName + "\t|\tURI: " + namespaceUri + "\n");
+                        Debug.WriteLine($"Name: {localName}\t|\tURI: {namespaceUri}\n");
 
                         // in which axisFields got updated
                         constraintStructures[j].axisSelector.PushKS(_positionInfo.LineNumber, _positionInfo.LinePosition);
@@ -2366,7 +2366,7 @@ private void AttributeIdentityConstraints(string name, string? ns, object obj, s
                             //attribute is only simpletype, so needn't checking...
                             // can fill value here, yeah!!
                             Debug.WriteLine("Attribute Field Filling Value!");
-                            Debug.WriteLine("Name: " + name + "\t|\tURI: " + ns + "\t|\tValue: " + obj + "\n");
+                            Debug.WriteLine($"Name: {name}\t|\tURI: {ns}\t|\tValue: {obj}\n");
                             if (laxis.Ks[laxis.Column] != null)
                             {
                                 // should be evaluated to either an empty node-set or a node-set with exactly one member
@@ -2411,7 +2411,7 @@ private void EndElementIdentityConstraints(object typedValue, string stringValue
                         if (laxis.isMatched)
                         {
                             Debug.WriteLine("Element Field Filling Value!");
-                            Debug.WriteLine("Name: " + localName + "\t|\tURI: " + namespaceUri + "\t|\tValue: " + typedValue + "\n");
+                            Debug.WriteLine($"Name: {localName}\t|\tURI: {namespaceUri}\t|\tValue: {typedValue}\n");
                             // fill value
                             laxis.isMatched = false;
                             if (laxis.Ks[laxis.Column] != null)
@@ -2821,7 +2821,7 @@ private static void EnumerateAny(StringBuilder builder, string namespaces)
 
         internal static string QNameString(string localName, string ns)
         {
-            return (ns.Length != 0) ? string.Concat(ns, ":", localName) : localName;
+            return (ns.Length != 0) ? $"{ns}:{localName}" : localName;
         }
 
         internal static string BuildElementName(XmlQualifiedName qname)

src/libraries/System.Private.Xml/src/System/Xml/Schema/XmlValueConverter.cs

@@ -264,7 +264,7 @@ protected XmlBaseConverter(XmlTypeCode typeCode)
                     break;
 
                 default:
-                    Debug.Fail("Type code " + typeCode + " is not supported.");
+                    Debug.Fail($"Type code {typeCode} is not supported.");
                     break;
             }
 
@@ -475,15 +475,15 @@ protected static string QNameToString(XmlQualifiedName name)
             }
             else if (name.Namespace == XmlReservedNs.NsXs)
             {
-                return "xs:" + name.Name;
+                return $"xs:{name.Name}";
             }
             else if (name.Namespace == XmlReservedNs.NsXQueryDataType)
             {
-                return "xdt:" + name.Name;
+                return $"xdt:{name.Name}";
             }
             else
             {
-                return "{" + name.Namespace + "}" + name.Name;
+                return $"{{{name.Namespace}}}{name.Name}";
             }
         }
 
@@ -745,13 +745,13 @@ protected static string QNameToString(XmlQualifiedName qname, IXmlNamespaceResol
             string? prefix;
 
             if (nsResolver == null)
-                return string.Concat("{", qname.Namespace, "}", qname.Name);
+                return $"{{{qname.Namespace}}}{qname.Name}";
 
             prefix = nsResolver.LookupPrefix(qname.Namespace);
             if (prefix == null)
                 throw new InvalidCastException(SR.Format(SR.XmlConvert_TypeNoPrefix, qname, qname.Namespace));
 
-            return (prefix.Length != 0) ? string.Concat(prefix, ":", qname.Name) : qname.Name;
+            return (prefix.Length != 0) ? $"{prefix}:{qname.Name}" : qname.Name;
         }
 
         protected static string TimeToString(DateTime value)

src/libraries/System.Private.Xml/src/System/Xml/Schema/XsdBuilder.cs

@@ -970,7 +970,7 @@ private XmlSchemaObject GetContainer(State state)
                     container = _redefine!;
                     break;
                 default:
-                    Debug.Fail("State is " + state);
+                    Debug.Fail($"State is {state}");
                     break;
             }
             return container;
@@ -1095,7 +1095,7 @@ private void SetContainer(State state, object container)
                     _redefine = (XmlSchemaRedefine)container;
                     break;
                 default:
-                    Debug.Fail("State is " + state);
+                    Debug.Fail($"State is {state}");
                     break;
             }
         }