DataRowComparer.cs source code in C# .NET

                        Code:
                         / 4.0 / 4.0 / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / DataSet / System / Data / DataRowComparer.cs / 1305376 / DataRowComparer.cs
                        
                        
                            //------------------------------------------------------------------------------ 
// 
//     Copyright (c) Microsoft Corporation.  All rights reserved.
// 
// [....] 
// spather
//----------------------------------------------------------------------------- 
using System; 
using System.Data;
using System.Collections; 
using System.Collections.Generic;
using System.Diagnostics;
using System.Data.DataSetExtensions;
 
namespace System.Data
{ 
    ///  
    /// This class implements IEqualityComparer using value based semantics
    /// when comparing DataRows. 
    /// 
    public static class DataRowComparer
    {
        ///  
        /// Gets the singleton instance of the data row comparer.
        ///  
        public static DataRowComparer Default { get { return DataRowComparer.Default; } } 

        internal static bool AreEqual(object a, object b) 
        {
            if (Object.ReferenceEquals(a, b))
            {   // same reference or (null, null) or (DBNull.Value, DBNull.Value)
                return true; 
            }
            if (Object.ReferenceEquals(a, null) || Object.ReferenceEquals(a, DBNull.Value) || 
                Object.ReferenceEquals(b, null) || Object.ReferenceEquals(b, DBNull.Value)) 
            {   // (null, non-null) or (null, DBNull.Value) or vice versa
                return false; 
            }
            return (a.Equals(b) || (a.GetType().IsArray && CompareArray((Array)a, b as Array)));
        }
 
        private static bool AreElementEqual(object a, object b)
        { 
            if (Object.ReferenceEquals(a, b)) 
            {   // same reference or (null, null) or (DBNull.Value, DBNull.Value)
                return true; 
            }
            if (Object.ReferenceEquals(a, null) || Object.ReferenceEquals(a, DBNull.Value) ||
                Object.ReferenceEquals(b, null) || Object.ReferenceEquals(b, DBNull.Value))
            {   // (null, non-null) or (null, DBNull.Value) or vice versa 
                return false;
            } 
            return a.Equals(b); 
        }
 
        private static bool CompareArray(Array a, Array b)
        {
            if ((null == b) ||
                (1 != a.Rank) || 
                (1 != b.Rank) ||
                (a.Length != b.Length)) 
            {   // automatically consider array's with Rank>1 not-equal 
                return false;
            } 

            int index1 = a.GetLowerBound(0);
            int index2 = b.GetLowerBound(0);
            if (a.GetType() == b.GetType() && (0 == index1) && (0 == index2)) 
            {
                switch (Type.GetTypeCode(a.GetType().GetElementType())) 
                { 
                    case TypeCode.Byte:
                        return DataRowComparer.CompareEquatableArray((Byte[])a, (Byte[])b); 
                    case TypeCode.Int16:
                        return DataRowComparer.CompareEquatableArray((Int16[])a, (Int16[])b);
                    case TypeCode.Int32:
                        return DataRowComparer.CompareEquatableArray((Int32[])a, (Int32[])b); 
                    case TypeCode.Int64:
                        return DataRowComparer.CompareEquatableArray((Int64[])a, (Int64[])b); 
                    case TypeCode.String: 
                        return DataRowComparer.CompareEquatableArray((String[])a, (String[])b);
                } 
            }

            //Compare every element. But don't recurse if we have Array of array.
            int length = index1 + a.Length; 
            for (; index1 < length; ++index1, ++index2)
            { 
                if (!AreElementEqual(a.GetValue(index1), b.GetValue(index2))) 
                {
                    return false; 
                }
            }
            return true;
        } 

        private static bool CompareEquatableArray(TElem[] a, TElem[] b) where TElem : IEquatable 
        { 
            if (Object.ReferenceEquals(a, b))
            { 
                return true;
            }
            if (Object.ReferenceEquals(a, null) ||
                Object.ReferenceEquals(b, null)) 
            {
                return false; 
            } 
            if (a.Length != b.Length)
            { 
                return false;
            }

            for (int i = 0; i < a.Length; ++i) 
            {
                if (!a[i].Equals(b[i])) 
                { 
                    return false;
                } 
            }
            return true;
        }
    } 

    ///  
    /// This class implements IEqualityComparer using value based semantics 
    /// when comparing DataRows.
    ///  
    public sealed class DataRowComparer : IEqualityComparer where TRow : DataRow
    {
        /// 
        /// Private constructor to prevent initialization outside of Default singleton instance. 
        /// 
        private DataRowComparer() { } 
 
        private static DataRowComparer _instance = new DataRowComparer();
 
        /// 
        /// Gets the singleton instance of the data row comparer.
        /// 
        public static DataRowComparer Default { get { return _instance; } } 

        ///  
        /// This method compares to DataRows by doing a column by column value based 
        /// comparision.
        ///  
        /// 
        ///   The first input DataRow
        /// 
        ///  
        ///   The second input DataRow
        ///  
        ///  
        ///   True if rows are equal, false if not.
        ///  
        public bool Equals(TRow leftRow, TRow rightRow)
        {
            if (Object.ReferenceEquals(leftRow, rightRow))
            { 
                return true;
            } 
            if (Object.ReferenceEquals(leftRow, null) || 
                Object.ReferenceEquals(rightRow, null))
            { 
                return false;
            }

            if (leftRow.RowState == DataRowState.Deleted || rightRow.RowState == DataRowState.Deleted) 
            {
                throw DataSetUtil.InvalidOperation(Strings.DataSetLinq_CannotCompareDeletedRow); 
            } 

            int count = leftRow.Table.Columns.Count; 
            if (count != rightRow.Table.Columns.Count)
            {
                return false;
            } 

            for (int i = 0; i < count; ++i) 
            { 
                if (!DataRowComparer.AreEqual(leftRow[i], rightRow[i]))
                { 
                    return false;
                }
            }
            return true; 
        }
 
        ///  
        /// This mtheod retrieves a hash code for the source row.
        ///  
        /// 
        ///   The source DataRow
        /// 
        ///  
        ///   HashCode for row based on values in the row.
        ///  
        public int GetHashCode(TRow row) 
        {
            DataSetUtil.CheckArgumentNull(row, "row"); 

            if (row.RowState == DataRowState.Deleted)
            {
                throw DataSetUtil.InvalidOperation(Strings.DataSetLinq_CannotCompareDeletedRow); 
            }
 
            int hash = 0; 
            Debug.Assert(row.Table != null);
            if (row.Table.Columns.Count > 0) 
            {
                // if the row has at least one column, then use the first column value
                object value = row[0];
 
                Type valueType = value.GetType();
                if (valueType.IsArray) 
                { 
                    Array array = value as Array;
 
                    if (array.Rank > 1)
                    {
                        hash = value.GetHashCode();
                    } 
                    else if (array.Length > 0)
                    { 
                        hash = array.GetValue(array.GetLowerBound(0)).GetHashCode(); 
                    }
                } 
                else
                {
                    System.ValueType vt = value as System.ValueType;
 
                    // have to unbox value types.
                    if (vt != null) 
                    { 
                        hash = vt.GetHashCode();
                    } 
                    else
                    {
                        hash = value.GetHashCode();
                    } 
                }
            } 
            // if table has no columns, the hash code is 0 
            return hash;
        } 
    }
}

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
//------------------------------------------------------------------------------ 
// 
//     Copyright (c) Microsoft Corporation.  All rights reserved.
// 
// [....] 
// spather
//----------------------------------------------------------------------------- 
using System; 
using System.Data;
using System.Collections; 
using System.Collections.Generic;
using System.Diagnostics;
using System.Data.DataSetExtensions;
 
namespace System.Data
{ 
    ///  
    /// This class implements IEqualityComparer using value based semantics
    /// when comparing DataRows. 
    /// 
    public static class DataRowComparer
    {
        ///  
        /// Gets the singleton instance of the data row comparer.
        ///  
        public static DataRowComparer Default { get { return DataRowComparer.Default; } } 

        internal static bool AreEqual(object a, object b) 
        {
            if (Object.ReferenceEquals(a, b))
            {   // same reference or (null, null) or (DBNull.Value, DBNull.Value)
                return true; 
            }
            if (Object.ReferenceEquals(a, null) || Object.ReferenceEquals(a, DBNull.Value) || 
                Object.ReferenceEquals(b, null) || Object.ReferenceEquals(b, DBNull.Value)) 
            {   // (null, non-null) or (null, DBNull.Value) or vice versa
                return false; 
            }
            return (a.Equals(b) || (a.GetType().IsArray && CompareArray((Array)a, b as Array)));
        }
 
        private static bool AreElementEqual(object a, object b)
        { 
            if (Object.ReferenceEquals(a, b)) 
            {   // same reference or (null, null) or (DBNull.Value, DBNull.Value)
                return true; 
            }
            if (Object.ReferenceEquals(a, null) || Object.ReferenceEquals(a, DBNull.Value) ||
                Object.ReferenceEquals(b, null) || Object.ReferenceEquals(b, DBNull.Value))
            {   // (null, non-null) or (null, DBNull.Value) or vice versa 
                return false;
            } 
            return a.Equals(b); 
        }
 
        private static bool CompareArray(Array a, Array b)
        {
            if ((null == b) ||
                (1 != a.Rank) || 
                (1 != b.Rank) ||
                (a.Length != b.Length)) 
            {   // automatically consider array's with Rank>1 not-equal 
                return false;
            } 

            int index1 = a.GetLowerBound(0);
            int index2 = b.GetLowerBound(0);
            if (a.GetType() == b.GetType() && (0 == index1) && (0 == index2)) 
            {
                switch (Type.GetTypeCode(a.GetType().GetElementType())) 
                { 
                    case TypeCode.Byte:
                        return DataRowComparer.CompareEquatableArray((Byte[])a, (Byte[])b); 
                    case TypeCode.Int16:
                        return DataRowComparer.CompareEquatableArray((Int16[])a, (Int16[])b);
                    case TypeCode.Int32:
                        return DataRowComparer.CompareEquatableArray((Int32[])a, (Int32[])b); 
                    case TypeCode.Int64:
                        return DataRowComparer.CompareEquatableArray((Int64[])a, (Int64[])b); 
                    case TypeCode.String: 
                        return DataRowComparer.CompareEquatableArray((String[])a, (String[])b);
                } 
            }

            //Compare every element. But don't recurse if we have Array of array.
            int length = index1 + a.Length; 
            for (; index1 < length; ++index1, ++index2)
            { 
                if (!AreElementEqual(a.GetValue(index1), b.GetValue(index2))) 
                {
                    return false; 
                }
            }
            return true;
        } 

        private static bool CompareEquatableArray(TElem[] a, TElem[] b) where TElem : IEquatable 
        { 
            if (Object.ReferenceEquals(a, b))
            { 
                return true;
            }
            if (Object.ReferenceEquals(a, null) ||
                Object.ReferenceEquals(b, null)) 
            {
                return false; 
            } 
            if (a.Length != b.Length)
            { 
                return false;
            }

            for (int i = 0; i < a.Length; ++i) 
            {
                if (!a[i].Equals(b[i])) 
                { 
                    return false;
                } 
            }
            return true;
        }
    } 

    ///  
    /// This class implements IEqualityComparer using value based semantics 
    /// when comparing DataRows.
    ///  
    public sealed class DataRowComparer : IEqualityComparer where TRow : DataRow
    {
        /// 
        /// Private constructor to prevent initialization outside of Default singleton instance. 
        /// 
        private DataRowComparer() { } 
 
        private static DataRowComparer _instance = new DataRowComparer();
 
        /// 
        /// Gets the singleton instance of the data row comparer.
        /// 
        public static DataRowComparer Default { get { return _instance; } } 

        ///  
        /// This method compares to DataRows by doing a column by column value based 
        /// comparision.
        ///  
        /// 
        ///   The first input DataRow
        /// 
        ///  
        ///   The second input DataRow
        ///  
        ///  
        ///   True if rows are equal, false if not.
        ///  
        public bool Equals(TRow leftRow, TRow rightRow)
        {
            if (Object.ReferenceEquals(leftRow, rightRow))
            { 
                return true;
            } 
            if (Object.ReferenceEquals(leftRow, null) || 
                Object.ReferenceEquals(rightRow, null))
            { 
                return false;
            }

            if (leftRow.RowState == DataRowState.Deleted || rightRow.RowState == DataRowState.Deleted) 
            {
                throw DataSetUtil.InvalidOperation(Strings.DataSetLinq_CannotCompareDeletedRow); 
            } 

            int count = leftRow.Table.Columns.Count; 
            if (count != rightRow.Table.Columns.Count)
            {
                return false;
            } 

            for (int i = 0; i < count; ++i) 
            { 
                if (!DataRowComparer.AreEqual(leftRow[i], rightRow[i]))
                { 
                    return false;
                }
            }
            return true; 
        }
 
        ///  
        /// This mtheod retrieves a hash code for the source row.
        ///  
        /// 
        ///   The source DataRow
        /// 
        ///  
        ///   HashCode for row based on values in the row.
        ///  
        public int GetHashCode(TRow row) 
        {
            DataSetUtil.CheckArgumentNull(row, "row"); 

            if (row.RowState == DataRowState.Deleted)
            {
                throw DataSetUtil.InvalidOperation(Strings.DataSetLinq_CannotCompareDeletedRow); 
            }
 
            int hash = 0; 
            Debug.Assert(row.Table != null);
            if (row.Table.Columns.Count > 0) 
            {
                // if the row has at least one column, then use the first column value
                object value = row[0];
 
                Type valueType = value.GetType();
                if (valueType.IsArray) 
                { 
                    Array array = value as Array;
 
                    if (array.Rank > 1)
                    {
                        hash = value.GetHashCode();
                    } 
                    else if (array.Length > 0)
                    { 
                        hash = array.GetValue(array.GetLowerBound(0)).GetHashCode(); 
                    }
                } 
                else
                {
                    System.ValueType vt = value as System.ValueType;
 
                    // have to unbox value types.
                    if (vt != null) 
                    { 
                        hash = vt.GetHashCode();
                    } 
                    else
                    {
                        hash = value.GetHashCode();
                    } 
                }
            } 
            // if table has no columns, the hash code is 0 
            return hash;
        } 
    }
}

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

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