'4'和'4'在主键中发生冲突,但在文件系统中不发生冲突

Question

DataTable有主键来存储有关文件的信息.恰好有2个文件的名称与符号'4'和'4'(0xff14,"全宽数字四"符号)不同.由于唯一性失败,DataTable无法包含它们.但是,在Windows文件系统中,它们似乎能够共存而没有任何问题.

这种行为似乎不依赖于语言环境设置,我将"Region&Language-> Formats-> Format"从英语更改为日语,"非unicode程序语言"也发生了变化.Locale打印为"jp-JP","en-GB".总是一样的结果.

问题:

1. 修复它的方法会不那么干扰？我可以切换到使用容器而不是System.Data.*但我想避免它.是否可以为列定义自定义比较器或以其他方式更好地检查唯一性？启用区分大小写(将解决此问题)会导致其他问题.
2. 某些全局设置是否有可能在不重建软件的情况下修复它？

失败的演示程序:

using System;
using System.Data;

namespace DataTableUniqueness
{
    class Program
    {
        static void Main(string[] args)
        {
            var changes = new DataTable("Rows");

            var column = new DataColumn { DataType = Type.GetType("System.String"), ColumnName = "File" };
            changes.Columns.Add(column);
            var primKey = new DataColumn[1];
            primKey[0] = column;
            changes.PrimaryKey = primKey;

            changes.Rows.Add("4.txt");
            try
            {
                changes.Rows.Add("?.txt"); // throws the exception
            }
            catch (Exception e)
            {
                Console.WriteLine("Exception: {0}", e);
            }
        }
    }
}

例外

Exception: System.Data.ConstraintException: Column 'File' is constrained to be unique.  Value '4.txt' is already present.
   at System.Data.UniqueConstraint.CheckConstraint(DataRow row, DataRowAction action)
   at System.Data.DataTable.RaiseRowChanging(DataRowChangeEventArgs args, DataRow eRow, DataRowAction eAction, Boolean fireEvent)
   at System.Data.DataTable.SetNewRecordWorker(DataRow row, Int32 proposedRecord, DataRowAction action, Boolean isInMerge, Boolean suppressEnsurePropertyChanged, Int32 position, Boolean fireEvent, Exception& deferredException)
   at System.Data.DataTable.InsertRow(DataRow row, Int64 proposedID, Int32 pos, Boolean fireEvent)
   at System.Data.DataRowCollection.Add(Object[] values)

PS:该区域设置被视为:

Answer 1

通过使用DataType = typeof(object)"禁用"字符串规范化.字符串相等性仍用于比较.我不知道是否还有其他副作用.

更复杂的解决方案:为string类实现"包装器" :

public class MyString : IEquatable<MyString>, IComparable, IComparable<MyString>
{
    public static readonly StringComparer Comparer = StringComparer.InvariantCultureIgnoreCase;
    public readonly string Value;

    public MyString(string value)
    {
        Value = value;
    }

    public static implicit operator MyString(string value)
    {
        return new MyString(value);
    }

    public static implicit operator string(MyString value)
    {
        return value != null ? value.Value : null;
    }

    public override int GetHashCode()
    {
        return Comparer.GetHashCode(Value);
    }

    public override bool Equals(object obj)
    {
        if (obj == null || !(obj is MyString))
        {
            return false;
        }

        return Comparer.Equals(Value, ((MyString)obj).Value);
    }

    public override string ToString()
    {
        return Value != null ? Value.ToString() : null;
    }

    public bool Equals(MyString other)
    {
        if (other == null)
        {
            return false;
        }

        return Comparer.Equals(Value, other.Value);
    }

    public int CompareTo(object obj)
    {
        if (obj == null)
        {
            return 1;
        }

        return CompareTo((MyString)obj);
    }

    public int CompareTo(MyString other)
    {
        if (other == null)
        {
            return 1;
        }

        return Comparer.Compare(Value, other.Value);
    }
}

然后:

var changes = new DataTable("Rows");

var column = new DataColumn { DataType = typeof(MyString), ColumnName = "File" };
changes.Columns.Add(column);
var primKey = new DataColumn[1];
primKey[0] = column;
changes.PrimaryKey = primKey;

changes.Rows.Add((MyString)"a");
changes.Rows.Add((MyString)"4.txt");
try
{
    changes.Rows.Add((MyString)"?.txt"); // throws the exception
}
catch (Exception e)
{
    Console.WriteLine("Exception: {0}", e);
}

var row = changes.Rows.Find((MyString)"A");