Imported Upstream version 4.6.0.125

Former-commit-id: a2155e9bd80020e49e72e86c44da02a8ac0e57a4

mcs/class/referencesource/System.Data/System/Data/ConstraintEnumerator.cs

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+//------------------------------------------------------------------------------
+// <copyright file="ConstraintEnumerator.cs" company="Microsoft">
+//     Copyright (c) Microsoft Corporation.  All rights reserved.
+// </copyright>                                                                
+// <owner current="true" primary="true">[....]</owner>
+// <owner current="true" primary="false">[....]</owner>
+// <owner current="false" primary="false">[....]</owner>
+//------------------------------------------------------------------------------
+
+namespace System.Data {
+    using System;
+    using System.Diagnostics;
+    using System.Collections;
+    using System.ComponentModel;
+
+    /// <devdoc>
+    /// ConstraintEnumerator is an object for enumerating all constraints in a DataSet
+    /// </devdoc>
+    internal class ConstraintEnumerator {
+
+        System.Collections.IEnumerator tables;
+        System.Collections.IEnumerator constraints;
+        Constraint currentObject; 
+
+        public ConstraintEnumerator(DataSet dataSet) {
+            tables = (dataSet != null) ? dataSet.Tables.GetEnumerator() : null;
+            currentObject = null;
+        }
+
+        public bool GetNext() {
+            Constraint candidate;
+            currentObject = null;
+            while (tables != null) {
+                if (constraints == null) {
+                    if (!tables.MoveNext()) {
+                        tables = null;
+                        return false;
+                    }
+                    constraints = ((DataTable)tables.Current).Constraints.GetEnumerator();
+                }
+
+                if (!constraints.MoveNext()) {
+                    constraints = null;
+                    continue;
+                }
+
+                Debug.Assert(constraints.Current is Constraint, "ConstraintEnumerator, contains object which is not constraint");
+                candidate = (Constraint)constraints.Current;
+                if (IsValidCandidate(candidate)) {
+                    currentObject = candidate;
+                    return true;
+                }
+
+            }
+            return false;
+        }
+
+        public Constraint GetConstraint() {
+            // If currentObject is null we are before first GetNext or after last GetNext--consumer is bad
+            Debug.Assert (currentObject != null, "GetObject should never be called w/ null currentObject.");
+            return currentObject;   
+        }
+
+        protected virtual bool IsValidCandidate(Constraint constraint) {
+            return true;
+        }
+
+        protected Constraint CurrentObject {
+            get {
+                return currentObject;
+            }
+        }
+
+    }
+
+    internal class ForeignKeyConstraintEnumerator : ConstraintEnumerator {
+
+        public ForeignKeyConstraintEnumerator(DataSet dataSet) : base(dataSet) {
+
+        }
+
+        protected override bool IsValidCandidate(Constraint constraint) {
+            return(constraint is ForeignKeyConstraint);
+        }
+
+        public ForeignKeyConstraint GetForeignKeyConstraint() {
+            // If CurrentObject is null we are before first GetNext or after last GetNext--consumer is bad
+            Debug.Assert (CurrentObject != null, "GetObject should never be called w/ null currentObject.");
+            return(ForeignKeyConstraint)CurrentObject;   
+        }
+    }
+
+    internal sealed class ChildForeignKeyConstraintEnumerator : ForeignKeyConstraintEnumerator {
+
+        // this is the table to do comparisons against
+        DataTable table;
+        public ChildForeignKeyConstraintEnumerator(DataSet dataSet, DataTable inTable) : base(dataSet) {
+            this.table = inTable;
+        }
+
+        protected override bool IsValidCandidate(Constraint constraint) {
+            return((constraint is ForeignKeyConstraint) && (((ForeignKeyConstraint)constraint).Table == table));
+        }
+    }
+
+    internal sealed class ParentForeignKeyConstraintEnumerator : ForeignKeyConstraintEnumerator {
+
+        // this is the table to do comparisons against
+        DataTable table;
+        public ParentForeignKeyConstraintEnumerator(DataSet dataSet, DataTable inTable) : base(dataSet) {
+            this.table = inTable;
+        }
+
+        protected override bool IsValidCandidate(Constraint constraint) {
+            return((constraint is ForeignKeyConstraint) && (((ForeignKeyConstraint)constraint).RelatedTable == table));
+        }
+    }
+}