ConstraintEnumerator.cs source code in C# .NET

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                         / DotNET / DotNET / 8.0 / untmp / whidbey / REDBITS / ndp / fx / src / Data / System / Data / ConstraintEnumerator.cs / 1 / ConstraintEnumerator.cs
                        
                        
                            //------------------------------------------------------------------------------ 
// 
//     Copyright (c) Microsoft Corporation.  All rights reserved.
// 
// [....] 
// [....]
// [....] 
//----------------------------------------------------------------------------- 

namespace System.Data { 
    using System;
    using System.Diagnostics;
    using System.Collections;
    using System.ComponentModel; 

    ///  
    /// ConstraintEnumerator is an object for enumerating all constraints in a DataSet 
    /// 
    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)); 
        } 
    }
} 

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
// Copyright (c) Microsoft Corporation. All rights reserved.
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ConstraintEnumerator.cs source code in C# .NET

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