diff --git a/src/System.Data.Common/src/System/Data/DataColumnCollection.cs b/src/System.Data.Common/src/System/Data/DataColumnCollection.cs
index 7598e2c59869..014ad8b400b0 100644
--- a/src/System.Data.Common/src/System/Data/DataColumnCollection.cs
+++ b/src/System.Data.Common/src/System/Data/DataColumnCollection.cs
@@ -802,11 +802,6 @@ private void OnCollectionChanged(CollectionChangeEventArgs ccevent)
         {
             _table.UpdatePropertyDescriptorCollectionCache();
 
-            if ((null != ccevent) && !_table.SchemaLoading && !_table.fInitInProgress)
-            {
-                DataColumn column = (DataColumn)ccevent.Element;
-            }
-
             CollectionChanged?.Invoke(this, ccevent);
         }
 
diff --git a/src/System.Data.Common/src/System/Data/XMLSchema.cs b/src/System.Data.Common/src/System/Data/XMLSchema.cs
index e88572c8f1f0..726c377f61e1 100644
--- a/src/System.Data.Common/src/System/Data/XMLSchema.cs
+++ b/src/System.Data.Common/src/System/Data/XMLSchema.cs
@@ -783,7 +783,8 @@ public void LoadSchema(XmlSchemaSet schemaSet, DataSet ds)
                     continue;
                 }
 
-                DataTable table = HandleTable(element);
+                _ = HandleTable(element);
+
             }
 
             if (_dsElement != null)
@@ -2364,7 +2365,6 @@ internal void HandleElementColumn(XmlSchemaElement elem, DataTable table, bool i
                 // it should be  user defined  Named  simple type
                 if (((XmlSchemaSimpleType)typeNode).Name != null && ((XmlSchemaSimpleType)typeNode).Name.Length != 0 && ((XmlSchemaSimpleType)typeNode).QualifiedName.Namespace != Keywords.XSDNS)
                 {
-                    string targetNamespace = XSDSchema.GetMsdataAttribute(typeNode, Keywords.TARGETNAMESPACE);
                     strType = ((XmlSchemaSimpleType)typeNode).QualifiedName.ToString(); // use qualifed name
                     type = ParseDataType(strType);
                 }
@@ -2536,7 +2536,6 @@ internal void HandleDataSet(XmlSchemaElement node, bool isNewDataSet)
         {
             string dsName = node.Name;
             string dsNamespace = node.QualifiedName.Namespace;
-            int initialTableCount = _ds.Tables.Count; // just use for inference backward compatablity
 
             List<DataTable> tableSequenceList = new List<DataTable>();
 
diff --git a/src/System.Data.Common/src/System/Data/xmlsaver.cs b/src/System.Data.Common/src/System/Data/xmlsaver.cs
index 59c86728cfe4..c8cee2a4d2c2 100644
--- a/src/System.Data.Common/src/System/Data/xmlsaver.cs
+++ b/src/System.Data.Common/src/System/Data/xmlsaver.cs
@@ -949,7 +949,7 @@ internal XmlElement SchemaTree(XmlDocument xd, DataTable dt)
             _sRoot = rootSchema;
             WriteSchemaRoot(xd, rootSchema, dt.Namespace);
 
-            XmlElement dsCompositor = FillDataSetElement(xd, null, dt);
+            _ = FillDataSetElement(xd, null, dt);
 
             _constraintSeparator = xd.CreateElement(Keywords.XSD_PREFIX, "SHOULDNOTBEHERE", Keywords.XSDNS);
             _dsElement.AppendChild(_constraintSeparator);
@@ -1493,8 +1493,7 @@ internal XmlElement HandleColumn(DataColumn col, XmlDocument dc, XmlElement sche
                     root.SetAttribute(Keywords.REF, _prefixes[col.Namespace] + ":" + col.EncodedColumnName);
                     if (col.Table.Namespace != _ds.Namespace)
                     {
-                        string prefix = (string)_prefixes[col.Namespace];
-                        XmlElement tNode = GetSchema(col.Table.Namespace);
+                        _ = GetSchema(col.Table.Namespace);
                     }
                 }
             }
@@ -2486,9 +2485,6 @@ private void GenerateRow(DataRow row)
 
             string tablePrefix = (table.Namespace.Length != 0) ? table.Prefix : string.Empty;
 
-            // read value if the TextOnly column (if any)
-            object val = (table.XmlText == null ? DBNull.Value : row[table.XmlText, DataRowVersion.Original]);
-
             //old row
             _xmlw.WriteStartElement(tablePrefix, row.Table.EncodedTableName, row.Table.Namespace);
 
@@ -2774,8 +2770,6 @@ internal void SaveDiffgramData(XmlWriter xw, Hashtable rowsOrder)
             _isDiffgram = true;
             _rowsOrder = rowsOrder;
 
-            int countTopTable = _topLevelTables.Length;
-
             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)