List
- FindIndex(Predicate
)方法 - FindIndex(Int32，Predicate
)方法 - FindIndex(Int32，Int32，Predicate
)方法
FindIndex(Predicate )方法
此方法用于搜索与指定谓词定义的条件匹配的元素，并返回整个List
Syntax: public int FindIndex (Predicate
Parameter:
match: It is the Predicate
返回值：如果找到，则返回匹配match定义的条件的元素的首次出现的索引。如果找不到，则返回-1。
异常：如果match为null，则此方法将提供ArgumentNullException。
例子：
// C# program to demonstrate the use of
// List.FindIndex (Predicate ) method
using System;
using System.Collections.Generic;
class GFG1 : IComparable {
public String gg
{
get;
set;
}
public int CompareTo(Object o)
{
GFG1 e = o as GFG1;
if (e == null)
throw new ArgumentException("Not valid object");
return gg.CompareTo(e.gg);
}
}
class GFG2 {
String s;
public GFG2(String ss)
{
s = ss;
}
public bool StartsWith(GFG1 e)
{
return e.gg.StartsWith(s, StringComparison.InvariantCultureIgnoreCase);
}
}
// Driver Class
class GFG3 {
// Main Method
public static void Main()
{
var e = new List();
// List elements
e.AddRange(new GFG1[] {
new GFG1{
gg = "c",
},
new GFG1{
gg = "c++",
},
new GFG1{
gg = "java",
},
new GFG1{
gg = "C#",
},
new GFG1{
gg = "Python",
},
new GFG1{
gg = "Perl",
},
});
e.Sort();
// sorts the list
var es = new GFG2("C");
Console.WriteLine("'C' starts at index "
+ e.FindIndex(es.StartsWith));
es = new GFG2("P");
Console.WriteLine("'P' starts at index " +
e.FindIndex(es.StartsWith));
}
}
'C' starts at index 0
'P' starts at index 4
FindIndex(Int32，Predicate )方法
此方法搜索与指定谓词定义的条件匹配的元素，并返回List中从指定索引延伸到最后一个元素的元素范围内第一次出现的索引。
Syntax: public int FindIndex (int startIndex, Predicate
Parameter:
startIndex: It is the zero-based starting index of the search.
match: It is the Predicate
返回值：如果找到，则此方法将返回与“ match”定义的条件相匹配的元素首次出现的索引。如果找不到，则返回-1。
例外情况：
- ArgumentNullException：如果匹配为null。
- ArgumentOutOfRangeException：如果startIndex超出List
的有效索引范围。
例子：
// C# program to demonstrate the use of
// List.FindIndex (Int32, Predicate ) method
using System;
using System.Collections.Generic;
class GFG1 : IComparable {
public String gg
{
get;
set;
}
public int CompareTo(Object o)
{
GFG1 e = o as GFG1;
return gg.CompareTo(e.gg);
}
}
class GFG2 {
String s;
public GFG2(String ss)
{
s = ss;
}
public bool StartsWith(GFG1 e)
{
return e.gg.StartsWith(s, StringComparison.InvariantCultureIgnoreCase);
}
}
// Driver Class
class GFG3 {
// Main Method
public static void Main()
{
var e = new List();
// List elements
e.AddRange(new GFG1[] {
new GFG1{
gg = "c",
},
new GFG1{
gg = "Python",
},
new GFG1{
gg = "Java",
},
new GFG1{
gg = "C#",
},
new GFG1{
gg = "Java",
},
new GFG1{
gg = "Perl",
},
});
// sorts the list
e.Sort();
var es = new GFG2("C");
// Search for c start from index 1
Console.WriteLine("Search for 'C' starts at index "
+ e.FindIndex(1, es.StartsWith));
es = new GFG2("J");
// search for j starts from index 2
Console.WriteLine("Search for 'J' starts at index "
+ e.FindIndex(2, es.StartsWith));
}
}
Search for 'C' starts at index 1
Search for 'J' starts at index 2
FindIndex(Int32，Int32，Predicate )方法
此方法搜索与指定谓词定义的条件相匹配的元素，并返回从指定索引开始并包含指定数量的元素的List中元素范围内的第一个从零开始的索引。
Syntax: public int FindIndex (int startIndex, int count, Predicate
Parameters:
startIndex: It is the zero-based starting index of the search.
count: It is the number of elements in the section to search.
match: It is the Predicate
返回值：如果找到，则此方法将返回与“ match”定义的条件相匹配的元素首次出现的索引。如果找不到，则返回-1。
例外情况：
- ArgumentNullException：如果匹配为null。
- ArgumentOutOfRangeException：如果startIndex超出List
的有效索引范围，或者count小于0或startIndex and count在List 中未指定有效部分。
例子：
// C# program to demonstrate the use of
// List.FindIndex (Int32, Int32,
// Predicate ) method
using System;
using System.Collections.Generic;
class GFG1 : IComparable {
public String gg
{
get;
set;
}
public int CompareTo(Object o)
{
GFG1 e = o as GFG1;
return gg.CompareTo(e.gg);
}
}
class GFG2 {
String s;
public GFG2(String ss)
{
s = ss;
}
public bool StartsWith(GFG1 e)
{
return e.gg.StartsWith(s, StringComparison.InvariantCultureIgnoreCase);
}
}
// Driver Class
class GFG3 {
// Main Method
public static void Main()
{
var e = new List();
// List elements
e.AddRange(new GFG1[] {
new GFG1{
gg = "c",
},
new GFG1{
gg = "Python",
},
new GFG1{
gg = "C++",
},
new GFG1{
gg = "Java",
},
new GFG1{
gg = "C#",
},
new GFG1{
gg = "Perl",
},
});
// sorts the list
e.Sort();
var es = new GFG2("C");
// search for c start from index 1
// count is 2 here
Console.WriteLine("Search for 'C' starts at index "
+ e.FindIndex(0, 2, es.StartsWith));
es = new GFG2("J");
// search for j starts from index 2
// count is 4 here
Console.WriteLine("Search for 'J' starts at index "
+ e.FindIndex(2, 4, es.StartsWith));
}
}
Search for 'C' starts at index 0
Search for 'J' starts at index 3
参考：
- https://docs.microsoft.com/zh-cn/dotnet/api/system.collections.generic.list-1.findindex?view=netframework-4.7.2