C# LINQ与IList<;SelectedItemList>;问题
我有一个Datatable,其中我需要将每一行转换为IListC# LINQ与IList<;SelectedItemList>;问题,c#,linq,C#,Linq,我有一个Datatable,其中我需要将每一行转换为IList public IList<SelectListItem> _area = new List<SelectListItem>(); public IList<SelectListItem> _team = new List<SelectListItem>(); foreach (DataRow row in dt.Rows) { _are
public IList<SelectListItem> _area = new List<SelectListItem>();
public IList<SelectListItem> _team = new List<SelectListItem>();
foreach (DataRow row in dt.Rows)
{
_area.Add(new SelectListItem() { Text = row[1].ToString(), Value = row[1].ToString() });
_team.Add(new SelectListItem() { Text = row[0].ToString(), Value = row[0].ToString() });
}
我需要使用LINQ来获得不同的值
我尝试过简单地使用:-
_area.Distinct();
但我只剩下32个我开始时使用的条目了???您是否尝试过这个
\u area=\u area.Distinct()代码>您是否尝试过此\u area=\u area.Distinct()代码>
这将为您提供区域的不同值
像这样怎么样
_area.GroupBy(x => x.Value).Select(x => x.First());
class Foo
{
public string Text { get; set; }
public string Value { get; set; }
public override bool Equals(object obj)
{
var foo = obj as Foo;
if(foo == null) return false;
return foo.Text == Text && foo.Value == Value;
}
public override int GetHashCode()
{
return Text.GetHashCode() * Value.GetHashCode() ^ 7;
}
}
你能更好地解释什么是Distinct吗?也许你应该重写Equals和GetHashCode,这样它就可以处理Distinct,类似这样的事情
_area.GroupBy(x => x.Value).Select(x => x.First());
class Foo
{
public string Text { get; set; }
public string Value { get; set; }
public override bool Equals(object obj)
{
var foo = obj as Foo;
if(foo == null) return false;
return foo.Text == Text && foo.Value == Value;
}
public override int GetHashCode()
{
return Text.GetHashCode() * Value.GetHashCode() ^ 7;
}
}
然后这将如您所期望的那样起作用(希望如此)
这将为您提供区域的不同值
像这样怎么样
_area.GroupBy(x => x.Value).Select(x => x.First());
class Foo
{
public string Text { get; set; }
public string Value { get; set; }
public override bool Equals(object obj)
{
var foo = obj as Foo;
if(foo == null) return false;
return foo.Text == Text && foo.Value == Value;
}
public override int GetHashCode()
{
return Text.GetHashCode() * Value.GetHashCode() ^ 7;
}
}
你能更好地解释什么是Distinct吗?也许你应该重写Equals和GetHashCode,这样它就可以处理Distinct,类似这样的事情
_area.GroupBy(x => x.Value).Select(x => x.First());
class Foo
{
public string Text { get; set; }
public string Value { get; set; }
public override bool Equals(object obj)
{
var foo = obj as Foo;
if(foo == null) return false;
return foo.Text == Text && foo.Value == Value;
}
public override int GetHashCode()
{
return Text.GetHashCode() * Value.GetHashCode() ^ 7;
}
}
然后这将如您所期望的那样起作用(希望如此)
Distinct()
方法采用类型为IEqualityComparer
的参数,因此在本例中,您可以创建一个相等比较器,比较两个SelectListItems
的两个值,如下所示:
public class SelectListItemComparer : IEqualityComparer<SelectListItem>
{
public static SelectListItemComparer Instance = new SelectListItemComparer();
private SelectListItemComparer() {}
public bool Equals(SelectListItem x, SelectListItem y)
{
return x.Value.Equals(y.Value);
}
public int GetHashCode(SelectListItem obj)
{
return obj.Value.GetHashCode();
}
}
var items = new[]
{
new SelectListItem {Text = "OMC", Value = "OMC"},
new SelectListItem {Text = "OMC", Value = "OMC"},
new SelectListItem {Text = "OMC", Value = "OMC"},
new SelectListItem {Text = "SIAM", Value = "SIAM"},
new SelectListItem {Text = "SIAM", Value = "SIAM"},
new SelectListItem {Text = "SIAM", Value = "SIAM"},
new SelectListItem {Text = "SIAM", Value = "SIAM"},
new SelectListItem {Text = "SIAM", Value = "SIAM"}
};
var comparer = new SelectListItemComparer();
var t1 = items.Distinct(SelectListItemComparer.Instance).ToList();
t1
现在只包含两个元素。Distinct()
方法采用类型为IEqualityComparer
的参数,因此在这种情况下,您可以创建一个相等比较器来比较两个SelectListItems
的两个值,如下所示:
public class SelectListItemComparer : IEqualityComparer<SelectListItem>
{
public static SelectListItemComparer Instance = new SelectListItemComparer();
private SelectListItemComparer() {}
public bool Equals(SelectListItem x, SelectListItem y)
{
return x.Value.Equals(y.Value);
}
public int GetHashCode(SelectListItem obj)
{
return obj.Value.GetHashCode();
}
}
var items = new[]
{
new SelectListItem {Text = "OMC", Value = "OMC"},
new SelectListItem {Text = "OMC", Value = "OMC"},
new SelectListItem {Text = "OMC", Value = "OMC"},
new SelectListItem {Text = "SIAM", Value = "SIAM"},
new SelectListItem {Text = "SIAM", Value = "SIAM"},
new SelectListItem {Text = "SIAM", Value = "SIAM"},
new SelectListItem {Text = "SIAM", Value = "SIAM"},
new SelectListItem {Text = "SIAM", Value = "SIAM"}
};
var comparer = new SelectListItemComparer();
var t1 = items.Distinct(SelectListItemComparer.Instance).ToList();
t1
现在将只包含两个元素。SelectedListItem不会覆盖Equals,对吗?您需要将其重新分配到\u区域
中,就像\u区域=\u区域.Distinct()
@Max一样,我认为您是对的。它应该覆盖HashCode到SelectedListItem不覆盖Equals,对吗?你需要像\u area=\u area.Distinct()一样将其重新分配到\u area
@Max,我想你是对的。它应该覆盖HashCode,因为它无法将IEnumerable转换为IlistI。我已经这样做了,它编译了,但是列表仍然有32个条目,这太奇怪了!无法将IEnumerable转换为IlistI。如果您完成了此操作,它会编译,但列表仍有32个条目,这太奇怪了!我不能这样做,它不允许我在选择命令后引用x我不能这样做,它不允许我在选择命令后引用x