Use string.IsNullOrEmpty and ArgumentException.ThrowIfNullOrEmpty in …

…many more places (#85858)

src/libraries/System.ComponentModel.TypeConverter/src/System/ComponentModel/MaskedTextProvider.cs

@@ -2710,7 +2710,7 @@ public bool VerifyString(string input, out int testPosition, out MaskedTextResul
         {
             testPosition = 0;
 
-            if (input == null || input.Length == 0) // nothing to verify.
+            if (string.IsNullOrEmpty(input)) // nothing to verify.
             {
                 resultHint = MaskedTextResultHint.NoEffect;
                 return true;

src/libraries/System.ComponentModel.TypeConverter/src/System/ComponentModel/PropertyDescriptor.cs

@@ -336,7 +336,7 @@ public virtual PropertyDescriptorCollection GetChildProperties(object? instance,
         protected Type? GetTypeFromName(
             [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicConstructors)] string? typeName)
         {
-            if (typeName == null || typeName.Length == 0)
+            if (string.IsNullOrEmpty(typeName))
             {
                 return null;
             }

src/libraries/System.ComponentModel.TypeConverter/src/System/ComponentModel/TypeDescriptor.cs

@@ -1136,7 +1136,7 @@ public static EventDescriptorCollection GetEvents(object component, Attribute[]?
                     name = component.Site.Name;
                 }
 
-                if (name == null || name.Length == 0)
+                if (string.IsNullOrEmpty(name))
                 {
                     int ci = System.Threading.Interlocked.Increment(ref s_collisionIndex) - 1;
                     name = ci.ToString(CultureInfo.InvariantCulture);

src/libraries/System.Data.Common/src/System/Data/Common/ObjectStorage.cs

@@ -359,7 +359,7 @@ public override object ConvertXmlToObject(XmlReader xmlReader, XmlRootAttribute?
             { // this means type implements IXmlSerializable
                 Type? type = null;
                 string? typeName = xmlReader.GetAttribute(Keywords.MSD_INSTANCETYPE, Keywords.MSDNS);
-                if (typeName == null || typeName.Length == 0)
+                if (string.IsNullOrEmpty(typeName))
                 { // No CDT polumorphism
                     string? xsdTypeName = xmlReader.GetAttribute(Keywords.TYPE, Keywords.XSINS); // this xsd type: Base type polymorphism
                     if (null != xsdTypeName && xsdTypeName.Length > 0)

src/libraries/System.Data.Common/src/System/Data/DataError.cs

@@ -39,7 +39,7 @@ internal void SetColumnError(DataColumn column, string? error)
         {
             Debug.Assert(column != null, "Invalid (null) argument");
             Debug.Assert(column.Table != null, "Invalid (loose) column");
-            if (error == null || error.Length == 0)
+            if (string.IsNullOrEmpty(error))
             {
                 // remove error from the collection
                 Clear(column);

src/libraries/System.Data.Common/src/System/Data/DataSet.cs

@@ -748,7 +748,7 @@ public string DataSetName
                 DataCommonEventSource.Log.Trace("<ds.DataSet.set_DataSetName|API> {0}, '{1}'", ObjectID, value);
                 if (value != _dataSetName)
                 {
-                    if (value == null || value.Length == 0)
+                    if (string.IsNullOrEmpty(value))
                     {
                         throw ExceptionBuilder.SetDataSetNameToEmpty();
                     }

src/libraries/System.Data.Common/src/System/Data/SimpleType.cs

@@ -229,7 +229,7 @@ internal XmlNode ToNode(XmlDocument dc, Hashtable prefixes, bool inRemoting)
         {
             XmlElement typeNode = dc.CreateElement(Keywords.XSD_PREFIX, Keywords.XSD_SIMPLETYPE, Keywords.XSDNS);
 
-            if (_name != null && _name.Length != 0)
+            if (!string.IsNullOrEmpty(_name))
             {
                 // this is a global type
                 typeNode.SetAttribute(Keywords.NAME, _name);

src/libraries/System.Data.Common/src/System/Data/XDRSchema.cs

@@ -41,7 +41,7 @@ internal void LoadSchema(XmlElement schemaRoot, DataSet ds)
 
             // Get Locale and CaseSensitive properties
 
-            if (_schemaName == null || _schemaName.Length == 0)
+            if (string.IsNullOrEmpty(_schemaName))
                 _schemaName = "NewDataSet";
 
             ds.Namespace = _schemaUri;
@@ -85,7 +85,7 @@ internal void LoadSchema(XmlElement schemaRoot, DataSet ds)
             if (FEqualIdentity(node, Keywords.XDR_ELEMENT, Keywords.XDRNS) ||
                 FEqualIdentity(node, Keywords.XDR_ATTRIBUTE, Keywords.XDRNS))
             {
-                if (strType == null || strType.Length == 0)
+                if (string.IsNullOrEmpty(strType))
                     return null;
 
                 // Find an ELEMENTTYPE or ATTRIBUTETYPE with name=strType
@@ -133,7 +133,7 @@ internal static bool IsTextOnlyContent(XmlElement node)
             Debug.Assert(FEqualIdentity(node, Keywords.XDR_ELEMENTTYPE, Keywords.XDRNS), $"Invalid node type {node.LocalName}");
 
             string value = node.GetAttribute(Keywords.CONTENT);
-            if (value == null || value.Length == 0)
+            if (string.IsNullOrEmpty(value))
             {
                 string type = node.GetAttribute(Keywords.DT_TYPE, Keywords.DTNS);
                 return !string.IsNullOrEmpty(type);
@@ -311,7 +311,7 @@ private static Type ParseDataType(string dt, string dtValues)
             }
 
             NameType nt = FindNameType(strType);
-            if (nt == s_enumerationNameType && (dtValues == null || dtValues.Length == 0))
+            if (nt == s_enumerationNameType && string.IsNullOrEmpty(dtValues))
                 throw ExceptionBuilder.MissingAttribute("type", Keywords.DT_VALUES);
             return nt.type;
         }
@@ -332,7 +332,7 @@ internal static string GetInstanceName(XmlElement node)
             else
             {
                 instanceName = node.GetAttribute(Keywords.TYPE);
-                if (instanceName == null || instanceName.Length == 0)
+                if (string.IsNullOrEmpty(instanceName))
                     throw ExceptionBuilder.MissingAttribute("Element", Keywords.TYPE);
             }
 
@@ -400,7 +400,7 @@ internal void HandleColumn(XmlElement node, DataTable table)
 
             strType = typeNode.GetAttribute(Keywords.DT_TYPE, Keywords.DTNS);
             strValues = typeNode.GetAttribute(Keywords.DT_VALUES, Keywords.DTNS);
-            if (strType == null || strType.Length == 0)
+            if (string.IsNullOrEmpty(strType))
             {
                 strType = string.Empty;
                 type = typeof(string);
@@ -480,7 +480,7 @@ internal void HandleColumn(XmlElement node, DataTable table)
                 column.Namespace = targetNamespace;
 
             table.Columns.Add(column);
-            if (strDefault != null && strDefault.Length != 0)
+            if (!string.IsNullOrEmpty(strDefault))
                 try
                 {
                     column.DefaultValue = SqlConvert.ChangeTypeForXML(strDefault, type);

src/libraries/System.Data.Common/src/System/Data/XMLSchema.cs

@@ -80,7 +80,7 @@ internal static bool FEqualIdentity(XmlNode? node, string name, string ns)
         internal static bool GetBooleanAttribute(XmlElement element, string attrName, string attrNS, bool defVal)
         {
             string value = element.GetAttribute(attrName, attrNS);
-            if (value == null || value.Length == 0)
+            if (string.IsNullOrEmpty(value))
             {
                 return defVal;
             }
@@ -447,22 +447,22 @@ internal void HandleRelation(XmlElement node, bool fNested)
             }
 
             parentName = node.GetAttribute(Keywords.MSD_PARENT, Keywords.MSDNS);
-            if (parentName == null || parentName.Length == 0)
+            if (string.IsNullOrEmpty(parentName))
                 throw ExceptionBuilder.RelationParentNameMissing(strName);
             parentName = XmlConvert.DecodeName(parentName);
 
             childName = node.GetAttribute(Keywords.MSD_CHILD, Keywords.MSDNS);
-            if (childName == null || childName.Length == 0)
+            if (string.IsNullOrEmpty(childName))
                 throw ExceptionBuilder.RelationChildNameMissing(strName);
             childName = XmlConvert.DecodeName(childName);
 
             value = node.GetAttribute(Keywords.MSD_PARENTKEY, Keywords.MSDNS);
-            if (value == null || value.Length == 0)
+            if (string.IsNullOrEmpty(value))
                 throw ExceptionBuilder.RelationTableKeyMissing(strName);
 
             parentNames = value.TrimEnd(null).Split(new char[] { Keywords.MSD_KEYFIELDSEP, Keywords.MSD_KEYFIELDOLDSEP });
             value = node.GetAttribute(Keywords.MSD_CHILDKEY, Keywords.MSDNS);
-            if (value == null || value.Length == 0)
+            if (string.IsNullOrEmpty(value))
                 throw ExceptionBuilder.RelationChildKeyMissing(strName);
 
             childNames = value.TrimEnd(null).Split(new char[] { Keywords.MSD_KEYFIELDSEP, Keywords.MSD_KEYFIELDOLDSEP });
@@ -666,7 +666,7 @@ public void LoadSchema(XmlSchemaSet schemaSet, DataSet ds)
             {
                 _schemaName = schemaRoot.Id;
 
-                if (_schemaName == null || _schemaName.Length == 0)
+                if (string.IsNullOrEmpty(_schemaName))
                 {
                     _schemaName = "NewDataSet";
                 }
@@ -1208,7 +1208,7 @@ internal static DataColumn[] BuildKey(XmlSchemaIdentityConstraint keyNode, DataT
         internal static bool GetBooleanAttribute(XmlSchemaAnnotated element, string attrName, bool defVal)
         {
             string? value = GetMsdataAttribute(element, attrName);
-            if (value == null || value.Length == 0)
+            if (string.IsNullOrEmpty(value))
             {
                 return defVal;
             }
@@ -1227,7 +1227,7 @@ internal static bool GetBooleanAttribute(XmlSchemaAnnotated element, string attr
         internal static string GetStringAttribute(XmlSchemaAnnotated element, string attrName, string defVal)
         {
             string? value = GetMsdataAttribute(element, attrName);
-            if (value == null || value.Length == 0)
+            if (string.IsNullOrEmpty(value))
             {
                 return defVal;
             }
@@ -1287,7 +1287,7 @@ internal void HandleKeyref(XmlSchemaKeyref keyref)
             if (table == null)
                 return;
 
-            if (refer == null || refer.Length == 0)
+            if (string.IsNullOrEmpty(refer))
                 throw ExceptionBuilder.MissingRefer(name);
 
             ConstraintTable? key = (ConstraintTable?)_constraintNodes![refer];
@@ -1321,7 +1321,7 @@ internal void HandleKeyref(XmlSchemaKeyref keyref)
             {
                 string relName = XmlConvert.DecodeName(GetStringAttribute(keyref, Keywords.MSD_RELATIONNAME, keyref.Name!));
 
-                if (relName == null || relName.Length == 0)
+                if (string.IsNullOrEmpty(relName))
                     relName = name;
 
                 int iExisting = fKey[0].Table!.DataSet!.Relations.InternalIndexOf(relName);
@@ -1383,7 +1383,7 @@ internal void HandleConstraint(XmlSchemaIdentityConstraint keyNode)
             string? name;
 
             name = XmlConvert.DecodeName(keyNode.Name);
-            if (name == null || name.Length == 0)
+            if (string.IsNullOrEmpty(name))
                 throw ExceptionBuilder.MissingAttribute(Keywords.NAME);
 
             if (_constraintNodes!.ContainsKey(name))
@@ -1930,10 +1930,10 @@ internal static bool IsXsdType(string name)
             if (_typeNs == Keywords.XSDNS)
                 return null;
             XmlSchemaAnnotated? typeNode;
-            if (_type == null || _type.Length == 0)
+            if (string.IsNullOrEmpty(_type))
             {
                 _type = isAttr ? attr!.RefName.Name : el!.RefName.Name;
-                if (_type == null || _type.Length == 0)
+                if (string.IsNullOrEmpty(_type))
                     typeNode = isAttr ? attr!.SchemaType : el!.SchemaType;
                 else
                     typeNode = isAttr ? FindTypeNode((XmlSchemaAnnotated)_attributes![attr!.RefName]!) : FindTypeNode((XmlSchemaAnnotated)_elementsTable![el!.RefName]!);
@@ -1956,7 +1956,7 @@ internal void HandleSimpleTypeSimpleContentColumn(XmlSchemaSimpleType typeNode,
             SimpleType? xsdType = null;
 
             //            if (typeNode.QualifiedName.Namespace != Keywords.XSDNS) { // this means UDSimpleType
-            if (typeNode.QualifiedName.Name != null && typeNode.QualifiedName.Name.Length != 0 && typeNode.QualifiedName.Namespace != Keywords.XSDNS)
+            if (!string.IsNullOrEmpty(typeNode.QualifiedName.Name) && typeNode.QualifiedName.Namespace != Keywords.XSDNS)
             { // this means UDSimpleType
                 xsdType = new SimpleType(typeNode);
                 strType = typeNode.QualifiedName.ToString(); // use qualified name
@@ -2212,7 +2212,7 @@ internal void HandleAttributeColumn(XmlSchemaAttribute attrib, DataTable table,
             {
                 XmlSchemaSimpleType node = (typeNode as XmlSchemaSimpleType)!;
                 xsdType = new SimpleType(node);
-                if (node.QualifiedName.Name != null && node.QualifiedName.Name.Length != 0 && node.QualifiedName.Namespace != Keywords.XSDNS)
+                if (!string.IsNullOrEmpty(node.QualifiedName.Name) && node.QualifiedName.Namespace != Keywords.XSDNS)
                 {
                     // this means UDSimpleType
                     strType = node.QualifiedName.ToString(); // use qualified name
@@ -2376,7 +2376,7 @@ internal void HandleElementColumn(XmlSchemaElement elem, DataTable table, bool i
                 xsdType = new SimpleType(simpleTypeNode!);
                 // ((XmlSchemaSimpleType)typeNode).Name != null && ((XmlSchemaSimpleType)typeNode).Name.Length != 0 check is for annonymos simple type,
                 // it should be  user defined  Named  simple type
-                if (((XmlSchemaSimpleType)typeNode).Name != null && ((XmlSchemaSimpleType)typeNode).Name!.Length != 0 && ((XmlSchemaSimpleType)typeNode).QualifiedName.Namespace != Keywords.XSDNS)
+                if (!string.IsNullOrEmpty(((XmlSchemaSimpleType)typeNode).Name) && ((XmlSchemaSimpleType)typeNode).QualifiedName.Namespace != Keywords.XSDNS)
                 {
                     strType = ((XmlSchemaSimpleType)typeNode).QualifiedName.ToString(); // use qualified name
                     type = ParseDataType(strType);
@@ -2582,13 +2582,13 @@ internal void HandleDataSet(XmlSchemaElement node, bool isNewDataSet)
 
             // reuse variable
             value = GetMsdataAttribute(node, Keywords.MSD_DATASETNAME);
-            if (value != null && value.Length != 0)
+            if (!string.IsNullOrEmpty(value))
             {
                 dsName = value;
             }
 
             value = GetMsdataAttribute(node, Keywords.MSD_DATASETNAMESPACE);
-            if (value != null && value.Length != 0)
+            if (!string.IsNullOrEmpty(value))
             {
                 dsNamespace = value;
             }
@@ -2597,7 +2597,7 @@ internal void HandleDataSet(XmlSchemaElement node, bool isNewDataSet)
             SetExtProperties(_ds, node.UnhandledAttributes);
 
 
-            if (dsName != null && dsName.Length != 0)
+            if (!string.IsNullOrEmpty(dsName))
                 _ds.DataSetName = XmlConvert.DecodeName(dsName);
 
             //            _ds.Namespace = node.QualifiedName.Namespace;

src/libraries/System.Data.Common/src/System/Data/xmlsaver.cs

@@ -1250,7 +1250,7 @@ internal void HandleColumnType(DataColumn col, XmlDocument dc, XmlElement root,
                     XmlNode type;
                     string? name = stNode.Name;
 
-                    if (name != null && name.Length != 0)
+                    if (!string.IsNullOrEmpty(name))
                     {
                         // For remoting, always need to work with root schema's namespace
                         string nSpace = (_schFormat != SchemaFormat.Remoting) ? stNode.Namespace :
@@ -1314,7 +1314,7 @@ internal void HandleColumnType(DataColumn col, XmlDocument dc, XmlElement root,
             else
             {
                 string typeName = XmlDataTypeName(col.DataType); // do not update the hashtable, as it will not write msdata:DataType
-                if (typeName == null || typeName.Length == 0)
+                if (string.IsNullOrEmpty(typeName))
                 {
                     if (col.DataType == typeof(Guid) || col.DataType == typeof(Type))
                     {
@@ -1812,7 +1812,7 @@ internal XmlElement HandleTable(DataTable table, XmlDocument dc, XmlElement sche
                 // the type for this element
                 DataColumn col = table.Columns[0];
                 string _typeName = XmlDataTypeName(col.DataType);
-                if (_typeName == null || _typeName.Length == 0)
+                if (string.IsNullOrEmpty(_typeName))
                 {
                     _typeName = Keywords.XSD_ANYTYPE;
                 }
@@ -2445,7 +2445,7 @@ private void GenerateTableErrors(DataTable table)
                     DataColumn column = table.Columns[colNum];
                     string error = row.GetColumnError(column);
                     string columnPrefix = (column.Namespace.Length != 0) ? column.Prefix : string.Empty;
-                    if (error == null || error.Length == 0)
+                    if (string.IsNullOrEmpty(error))
                     {
                         continue;
                     }
@@ -2770,7 +2770,7 @@ internal static bool RowHasErrors(DataRow row)
             {
                 DataColumn column = row.Table.Columns[colNum];
                 string error = row.GetColumnError(column);
-                if (error == null || error.Length == 0)
+                if (string.IsNullOrEmpty(error))
                 {
                     continue;
                 }
@@ -2794,7 +2794,7 @@ internal void SaveDiffgramData(XmlWriter xw, Hashtable rowsOrder)
 
             string prefix = (_ds != null) ? ((_ds.Namespace.Length == 0) ? "" : _ds.Prefix) : ((_dt!.Namespace.Length == 0) ? "" : _dt.Prefix);
 
-            if (_ds == null || _ds.DataSetName == null || _ds.DataSetName.Length == 0)
+            if (_ds == null || string.IsNullOrEmpty(_ds.DataSetName))
                 _xmlw.WriteStartElement(prefix, Keywords.DOCUMENTELEMENT, (_dt!.Namespace == null) ? "" : _dt.Namespace);
             else
                 _xmlw.WriteStartElement(prefix, XmlConvert.EncodeLocalName(_ds.DataSetName), _ds.Namespace);
@@ -2852,7 +2852,7 @@ internal void Save(XmlWriter xw, bool writeSchema)
                 }
                 else
                 {
-                    if (_ds.DataSetName == null || _ds.DataSetName.Length == 0)
+                    if (string.IsNullOrEmpty(_ds.DataSetName))
                         _xmlw.WriteStartElement(prefix, Keywords.DOCUMENTELEMENT, _ds.Namespace);
                     else
                         _xmlw.WriteStartElement(prefix, XmlConvert.EncodeLocalName(_ds.DataSetName), _ds.Namespace);