FieldNameLookup.cs source code in C# .NET

                        Code:
                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / DataEntity / System / Data / Common / FieldNameLookup.cs / 1305376 / FieldNameLookup.cs
                        
                        
                            //------------------------------------------------------------------------------ 
// 
//      Copyright (c) Microsoft Corporation.  All rights reserved.
// 
// [....] 
// [....]
//----------------------------------------------------------------------------- 
 

namespace System.Data 
{
    using System;
    using System.Collections;
    using System.ComponentModel; 
    using System.Data;
    using System.Data.Common; 
    using System.Diagnostics; 
    using System.Globalization;
    using System.Text; 

    internal sealed class FieldNameLookup { // V1.2.3300, MDAC 69015, 71470

        // hashtable stores the index into the _fieldNames, match via case-sensitive 
        private Hashtable _fieldNameLookup;
 
        // original names for linear searches when exact matches fail 
        private string[] _fieldNames;
 
        // if _defaultLocaleID is -1 then _compareInfo is initialized with InvariantCulture CompareInfo
        // otherwise it is specified by the server? for the correct compare info
        private CompareInfo _compareInfo;
        private int _defaultLocaleID; 

        public FieldNameLookup(System.Collections.ObjectModel.ReadOnlyCollection columnNames, int defaultLocaleID) { 
 
            int length = columnNames.Count;
            string[] fieldNames = new string[length]; 
            for (int i = 0; i < length; ++i) {
                fieldNames[i] = columnNames[i];
                Debug.Assert(null != fieldNames[i], "MDAC 66681");
            } 
            _fieldNames = fieldNames;
            _defaultLocaleID = defaultLocaleID; 
            GenerateLookup(); 
        }
 
        public FieldNameLookup(IDataRecord reader, int defaultLocaleID) { // V1.2.3300

            int length = reader.FieldCount;
            string[] fieldNames = new string[length]; 
            for (int i = 0; i < length; ++i) {
                fieldNames[i] = reader.GetName(i); 
                Debug.Assert(null != fieldNames[i], "MDAC 66681"); 
            }
            _fieldNames = fieldNames; 
            _defaultLocaleID = defaultLocaleID;
        }

        public int GetOrdinal(string fieldName) { // V1.2.3300 
            if (null == fieldName) {
                throw ADP.ArgumentNull("fieldName"); 
            } 
            int index = IndexOf(fieldName);
            if (-1 == index) { 
                throw ADP.IndexOutOfRange(fieldName);
            }
            return index;
        } 

        public int IndexOf(string fieldName) { // V1.2.3300 
            if (null == _fieldNameLookup) { 
                GenerateLookup();
            } 
            int index;
            object value = _fieldNameLookup[fieldName];
            if (null != value) {
                // via case sensitive search, first match with lowest ordinal matches 
                index = (int) value;
            } 
            else { 
                // via case insensitive search, first match with lowest ordinal matches
                index = LinearIndexOf(fieldName, CompareOptions.IgnoreCase); 
                if (-1 == index) {
                    // do the slow search now (kana, width insensitive comparison)
                    index = LinearIndexOf(fieldName, ADP.compareOptions);
                } 
            }
            return index; 
        } 

        private int LinearIndexOf(string fieldName, CompareOptions compareOptions) { 
            CompareInfo compareInfo = _compareInfo;
            if (null == compareInfo) {
                if (-1 != _defaultLocaleID) {
                    compareInfo = CompareInfo.GetCompareInfo(_defaultLocaleID); 
                }
                if (null == compareInfo) { 
                    compareInfo = CultureInfo.InvariantCulture.CompareInfo; 
                }
                _compareInfo = compareInfo; 
            }
            int length = _fieldNames.Length;
            for (int i = 0; i < length; ++i) {
                if (0 == compareInfo.Compare(fieldName, _fieldNames[i], compareOptions)) { 
                    _fieldNameLookup[fieldName] = i; // add an exact match for the future
                    return i; 
                } 
            }
            return -1; 
        }

        // RTM common code for generating Hashtable from array of column names
        private void GenerateLookup() { 
            int length = _fieldNames.Length;
            Hashtable hash = new Hashtable(length); 
 
            // via case sensitive search, first match with lowest ordinal matches
            for (int i = length-1; 0 <= i; --i) { 
                string fieldName = _fieldNames[i];
                hash[fieldName] = i;
            }
            _fieldNameLookup = hash; 
        }
    } 
} 

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

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