为什么是Convert ?ToDecimal返回不同的值
本文关键字:返回 ToDecimal Convert 为什么 | 更新日期: 2023-09-27 18:17:10
我希望有人能帮助我理解为什么转换。ToDecimal在linq内部使用时是舍入小数,在linq外部使用时,它不
给定以下DB:
CREATE TABLE [dbo].[Widgets](
[ID] [int] NOT NULL,
[WidgetName] [varchar](50) NOT NULL,
[UnitsAvailable] [int] NOT NULL,
[WeightInGrams] [decimal](10, 6) NULL
) ON [PRIMARY]
GO
INSERT [dbo].[Widgets] VALUES (1, N'Best thing ever', 100, CAST(10.000210 AS Decimal(10, 6)))
INSERT [dbo].[Widgets] VALUES (2, N'Next Best thing', 50, CAST(100.000151 AS Decimal(10, 6)))
INSERT [dbo].[Widgets] VALUES (3, N'The Other Model', 25, CAST(5.231651 AS Decimal(10, 6)))
代码:class Program
{
static void Main(string[] args)
{
Console.WriteLine("------Example 1--------");
LqToSqlDataContext _ctx = new LqToSqlDataContext();
List<Widget> inventory = (from c in _ctx.linqWidgets
select new Widget()
{
Id = c.ID,
Name = c.WidgetName,
UnitsOnHand = c.UnitsAvailable,
WeightInGrams = Convert.ToDecimal(c.WeightInGrams)
}).ToList();
foreach(Widget w in inventory)
{
Console.WriteLine(w.ToString());
}
Console.WriteLine("------Example 2--------");
var _linqInventory = _ctx.linqWidgets;
Widget temp = null;
foreach(linqWidget lw in _linqInventory)
{
temp = new Widget();
temp.Id = lw.ID;
temp.Name = lw.WidgetName;
temp.UnitsOnHand = lw.UnitsAvailable;
temp.WeightInGrams = Convert.ToDecimal(lw.WeightInGrams);
Console.WriteLine(temp.ToString());
}
Console.ReadLine();
}
}
class Widget
{
public int Id { get; set; }
public string Name { get; set; }
public int UnitsOnHand { get; set; }
public decimal WeightInGrams { get; set; }
public override string ToString()
{
return this.Id + "'t" + this.Name + "'t" + this.UnitsOnHand + "'t" + this.WeightInGrams;
}
}
输出------Example 1--------
1 Best thing ever 100 10.0002
2 Next Best thing 50 100.0002
3 The Other Model 25 5.2317
------Example 2--------
1 Best thing ever 100 10.000210
2 Next Best thing 50 100.000151
3 The Other Model 25 5.231651
因为LinqtoSql翻译Convert。ToDecimal转换为sql语句,如CONVERT(DECIMAL({someNumberLinqComesupWith}, 4)
因为c#的decimal
类型和数据库中的decimal
类型不一样。
可以看到,c# decimal
更准确。