XPathNodeIterator.cs source code in C# .NET

                        Code:
                         / Dotnetfx_Vista_SP2 / Dotnetfx_Vista_SP2 / 8.0.50727.4016 / DEVDIV / depot / DevDiv / releases / whidbey / NetFxQFE / ndp / fx / src / Xml / System / Xml / XPath / XPathNodeIterator.cs / 1 / XPathNodeIterator.cs
                        
                        
                            //------------------------------------------------------------------------------ 
// 
//     Copyright (c) Microsoft Corporation.  All rights reserved.
// 
// [....] 
//-----------------------------------------------------------------------------
 
namespace System.Xml.XPath { 
    using System;
    using System.Collections; 
    using System.Diagnostics;
    using System.Text;

    [DebuggerDisplay("Position={CurrentPosition}, Current={debuggerDisplayProxy}")] 
    public abstract class XPathNodeIterator : ICloneable, IEnumerable {
        internal int count = -1; 
 
        object ICloneable.Clone() { return this.Clone(); }
 
        public abstract XPathNodeIterator Clone();
        public abstract bool MoveNext();
        public abstract XPathNavigator Current { get; }
        public abstract int CurrentPosition { get; } 
        public virtual int Count {
            get { 
                if (count == -1) { 
                    XPathNodeIterator clone = this.Clone();
                    while(clone.MoveNext()) ; 
                    count = clone.CurrentPosition;
                }
                return count;
            } 
        }
        public virtual IEnumerator GetEnumerator() { 
            return new Enumerator(this); 
        }
 
        private object debuggerDisplayProxy { get { return Current == null ? null : (object)new XPathNavigator.DebuggerDisplayProxy(Current); } }

        /// 
        /// Implementation of a resetable enumerator that is linked to the XPathNodeIterator used to create it. 
        /// 
        private class Enumerator : IEnumerator { 
            private XPathNodeIterator original;     // Keep original XPathNodeIterator in case Reset() is called 
            private XPathNodeIterator current;
            private bool iterationStarted; 

            public Enumerator(XPathNodeIterator original) {
                this.original = original.Clone();
            } 

            public virtual object Current { 
                get { 
                    // 1. Do not reuse the XPathNavigator, as we do in XPathNodeIterator
                    // 2. Throw exception if current position is before first node or after the last node 
                    if (this.iterationStarted) {
                        // Current is null if iterator is positioned after the last node
                        if (this.current == null)
                            throw new InvalidOperationException(Res.GetString(Res.Sch_EnumFinished, string.Empty)); 

                        return this.current.Current.Clone(); 
                    } 

                    // User must call MoveNext before accessing Current property 
                    throw new InvalidOperationException(Res.GetString(Res.Sch_EnumNotStarted, string.Empty));
                }
            }
 
            public virtual bool MoveNext() {
                // Delegate to XPathNodeIterator 
                if (!this.iterationStarted) { 
                    // Reset iteration to original position
                    this.current = this.original.Clone(); 
                    this.iterationStarted = true;
                }

                if (this.current == null || !this.current.MoveNext()) { 
                    // Iteration complete
                    this.current = null; 
                    return false; 
                }
                return true; 
            }

            public virtual void Reset() {
                this.iterationStarted = false; 
            }
        } 
    } 
}

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
//------------------------------------------------------------------------------ 
// 
//     Copyright (c) Microsoft Corporation.  All rights reserved.
// 
// [....] 
//-----------------------------------------------------------------------------
 
namespace System.Xml.XPath { 
    using System;
    using System.Collections; 
    using System.Diagnostics;
    using System.Text;

    [DebuggerDisplay("Position={CurrentPosition}, Current={debuggerDisplayProxy}")] 
    public abstract class XPathNodeIterator : ICloneable, IEnumerable {
        internal int count = -1; 
 
        object ICloneable.Clone() { return this.Clone(); }
 
        public abstract XPathNodeIterator Clone();
        public abstract bool MoveNext();
        public abstract XPathNavigator Current { get; }
        public abstract int CurrentPosition { get; } 
        public virtual int Count {
            get { 
                if (count == -1) { 
                    XPathNodeIterator clone = this.Clone();
                    while(clone.MoveNext()) ; 
                    count = clone.CurrentPosition;
                }
                return count;
            } 
        }
        public virtual IEnumerator GetEnumerator() { 
            return new Enumerator(this); 
        }
 
        private object debuggerDisplayProxy { get { return Current == null ? null : (object)new XPathNavigator.DebuggerDisplayProxy(Current); } }

        /// 
        /// Implementation of a resetable enumerator that is linked to the XPathNodeIterator used to create it. 
        /// 
        private class Enumerator : IEnumerator { 
            private XPathNodeIterator original;     // Keep original XPathNodeIterator in case Reset() is called 
            private XPathNodeIterator current;
            private bool iterationStarted; 

            public Enumerator(XPathNodeIterator original) {
                this.original = original.Clone();
            } 

            public virtual object Current { 
                get { 
                    // 1. Do not reuse the XPathNavigator, as we do in XPathNodeIterator
                    // 2. Throw exception if current position is before first node or after the last node 
                    if (this.iterationStarted) {
                        // Current is null if iterator is positioned after the last node
                        if (this.current == null)
                            throw new InvalidOperationException(Res.GetString(Res.Sch_EnumFinished, string.Empty)); 

                        return this.current.Current.Clone(); 
                    } 

                    // User must call MoveNext before accessing Current property 
                    throw new InvalidOperationException(Res.GetString(Res.Sch_EnumNotStarted, string.Empty));
                }
            }
 
            public virtual bool MoveNext() {
                // Delegate to XPathNodeIterator 
                if (!this.iterationStarted) { 
                    // Reset iteration to original position
                    this.current = this.original.Clone(); 
                    this.iterationStarted = true;
                }

                if (this.current == null || !this.current.MoveNext()) { 
                    // Iteration complete
                    this.current = null; 
                    return false; 
                }
                return true; 
            }

            public virtual void Reset() {
                this.iterationStarted = false; 
            }
        } 
    } 
}

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
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XPathNodeIterator.cs source code in C# .NET

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