StringComparer.cs source code in C# .NET

                        Code:
                         / FXUpdate3074 / FXUpdate3074 / 1.1 / untmp / whidbey / QFE / ndp / clr / src / BCL / System / StringComparer.cs / 1 / StringComparer.cs
                        
                        
                            // Copyright (c) Microsoft Corporation. All rights reserved.

namespace System { 
    using System.Collections;
    using System.Collections.Generic;
    using System.Globalization;
 
    [Serializable]
[System.Runtime.InteropServices.ComVisible(true)] 
    public abstract class StringComparer : IComparer, IEqualityComparer, IComparer, IEqualityComparer{ 
        private static StringComparer _invariantCulture = new CultureAwareComparer(CultureInfo.InvariantCulture, false);
        private static StringComparer _invariantCultureIgnoreCase = new CultureAwareComparer(CultureInfo.InvariantCulture, true); 
        private static StringComparer _ordinal = new OrdinalComparer(false);
        private static StringComparer _ordinalIgnoreCase = new OrdinalComparer(true);

        public static StringComparer InvariantCulture { 
            get {
                return _invariantCulture; 
            } 
        }
 
        public static StringComparer InvariantCultureIgnoreCase {
            get {
                return _invariantCultureIgnoreCase;
            } 
        }
 
        public static StringComparer CurrentCulture { 
            get {
                return new CultureAwareComparer(CultureInfo.CurrentCulture, false); 
            }
        }

        public static StringComparer CurrentCultureIgnoreCase { 
            get {
                return new CultureAwareComparer(CultureInfo.CurrentCulture, true); 
            } 
        }
 
        public static StringComparer Ordinal {
            get {
                return _ordinal;
            } 
        }
 
        public static StringComparer OrdinalIgnoreCase { 
            get {
                return _ordinalIgnoreCase; 
            }
        }

        public static StringComparer Create(CultureInfo culture, bool ignoreCase) { 
                if( culture == null) {
                    throw new ArgumentNullException("culture"); 
                } 

                return new CultureAwareComparer(culture, ignoreCase); 
        }

        public int Compare(object x, object y) {
            if (x == y) return 0; 
            if (x == null) return -1;
            if (y == null) return 1; 
 
            String sa = x as String;
            if (sa != null) { 
                String sb = y as String;
                if( sb != null) {
                    return Compare(sa, sb);
                } 
            }
 
            IComparable ia = x as IComparable; 
            if (ia != null) {
                return ia.CompareTo(y); 
            }

            throw new ArgumentException(Environment.GetResourceString("Argument_ImplementIComparable"));
        } 

 
        public new bool Equals(Object x, Object y) { 
            if (x == y) return true;
            if (x == null || y == null) return false; 

            String sa = x as String;
            if (sa != null) {
                String sb = y as String; 
                if( sb != null) {
                    return Equals(sa, sb); 
                } 
            }
            return x.Equals(y); 
        }

        public int GetHashCode(object obj) {
            if( obj == null) { 
                throw new ArgumentNullException("obj");
            } 
 
            string s = obj as string;
            if( s != null) { 
                return GetHashCode(s);
            }
            return obj.GetHashCode();
        } 

        public abstract int Compare(String x, String y); 
        public abstract bool Equals(String x, String y); 
        public abstract int GetHashCode(string obj);
    } 

    [Serializable()]
    internal sealed class CultureAwareComparer : StringComparer {
         private CompareInfo _compareInfo; 
         private bool            _ignoreCase;
 
        internal CultureAwareComparer(CultureInfo culture, bool ignoreCase) { 
               _compareInfo = culture.CompareInfo;
               _ignoreCase = ignoreCase; 
        }

        public override int Compare(string x, string y) {
            if (Object.ReferenceEquals(x, y)) return 0; 
            if (x == null) return -1;
            if (y == null) return 1; 
            return _compareInfo.Compare(x, y, _ignoreCase? CompareOptions.IgnoreCase :  CompareOptions.None); 
        }
 
        public override bool Equals(string x, string y) {
            if (Object.ReferenceEquals(x ,y)) return true;
            if (x == null || y == null) return false;
 
            return (_compareInfo.Compare(x, y, _ignoreCase? CompareOptions.IgnoreCase :  CompareOptions.None) == 0);
        } 
 
        public override int GetHashCode(string obj) {
            if( obj == null) { 
                throw new ArgumentNullException("obj");
            }

            if( _ignoreCase) { 
                return _compareInfo.GetHashCodeOfString(obj, CompareOptions.IgnoreCase);
            } 
 
            return _compareInfo.GetHashCodeOfString(obj, CompareOptions.None);
        } 

        // Equals method for the comparer itself.
        public override bool Equals(Object obj){
            CultureAwareComparer comparer = obj as CultureAwareComparer; 
            if( comparer == null) {
                return false; 
            } 
            return (this._ignoreCase == comparer._ignoreCase) && ( this._compareInfo.Equals(comparer._compareInfo));
        } 

        public override int GetHashCode() {
            int hashCode = _compareInfo.GetHashCode() ;
            return _ignoreCase ? (~hashCode) : hashCode; 
        }
    } 
 

    // Provide x more optimal implementation of ordinal comparison. 
    [Serializable()]
    internal sealed class OrdinalComparer : StringComparer  {
        private bool            _ignoreCase;
 
        internal OrdinalComparer(bool ignoreCase) {
               _ignoreCase = ignoreCase; 
        } 

        public override int Compare(string x, string y) { 
            if (Object.ReferenceEquals(x, y)) return 0;
            if (x == null) return -1;
            if (y == null) return 1;
 
            if( _ignoreCase) {
                return TextInfo.CompareOrdinalIgnoreCase(x, y); 
            } 

            return String.CompareOrdinal(x, y); 
        }

        public override bool Equals(string x, string y) {
            if (Object.ReferenceEquals(x ,y)) return true; 
            if (x == null || y == null) return false;
 
            if( _ignoreCase) { 
                if( x.Length != y.Length) {
                    return false; 
                }
                return (TextInfo.CompareOrdinalIgnoreCase(x, y) == 0);
            }
            return x.Equals(y); 
        }
 
        public override int GetHashCode(string obj) { 
            if( obj == null) {
                throw new ArgumentNullException("obj"); 
            }

            if( _ignoreCase) {
                return TextInfo.GetHashCodeOrdinalIgnoreCase(obj); 
            }
 
            return obj.GetHashCode(); 
        }
 
        // Equals method for the comparer itself.
        public override bool Equals(Object obj){
            OrdinalComparer comparer = obj as OrdinalComparer;
            if( comparer == null) { 
                return false;
            } 
            return (this._ignoreCase == comparer._ignoreCase); 
        }
 
        public override int GetHashCode() {
            string name = "OrdinalComparer";
            int hashCode = name.GetHashCode();
            return _ignoreCase ? (~hashCode) : hashCode; 
        }
    } 
} 

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

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