LINQ 学习路程 -- 查询操作 Conversion Operators
2024-08-26 10:19:55
| Method | Description |
|---|---|
| AsEnumerable | Returns the input sequence as IEnumerable<t> |
| AsQueryable | Converts IEnumerable to IQueryable, to simulate a remote query provider |
| Cast | Coverts a non-generic collection to a generic collection (IEnumerable to IEnumerable<T>) |
| OfType | Filters a collection based on a specified type |
| ToArray | Converts a collection to an array |
| ToDictionary | Puts elements into a Dictionary based on key selector function |
| ToList | Converts collection to List |
| ToLookup | Groups elements into an Lookup<TKey,TElement> |
class Program
{ static void ReportTypeProperties<T>(T obj)
{
Console.WriteLine("Compile-time type: {0}", typeof(T).Name);
Console.WriteLine("Actual type: {0}", obj.GetType().Name);
} static void Main(string[] args)
{
Student[] studentArray = {
new Student() { StudentID = , StudentName = "John", Age = } ,
new Student() { StudentID = , StudentName = "Steve", Age = } ,
new Student() { StudentID = , StudentName = "Bill", Age = } ,
new Student() { StudentID = , StudentName = "Ram" , Age = } ,
new Student() { StudentID = , StudentName = "Ron" , Age = } ,
}; ReportTypeProperties( studentArray);
ReportTypeProperties(studentArray.AsEnumerable());
ReportTypeProperties(studentArray.AsQueryable());
}
} Cast
class Program
{
static void ReportTypeProperties<T>(T obj)
{
Console.WriteLine("Compile-time type: {0}", typeof(T).Name);
Console.WriteLine("Actual type: {0}", obj.GetType().Name);
}
static void Main(string[] args)
{
Student[] studentArray = {
new Student() { StudentID = 1, StudentName = "John", Age = 18 } ,
new Student() { StudentID = 2, StudentName = "Steve", Age = 21 } ,
new Student() { StudentID = 3, StudentName = "Bill", Age = 25 } ,
new Student() { StudentID = 4, StudentName = "Ram" , Age = 20 } ,
new Student() { StudentID = 5, StudentName = "Ron" , Age = 31 } ,
};
ReportTypeProperties( studentArray);
ReportTypeProperties(studentArray.Cast<Student>());
}
}
IList<string> strList = new List<string>() {
"One",
"Two",
"Three",
"Four",
"Three"
};
string[] strArray = strList.ToArray<string>();// converts List to Array
IList<string> list = strArray.ToList<string>(); // converts array into list
IList<Student> studentList = new List<Student>() {
new Student() { StudentID = 1, StudentName = "John", age = 18 } ,
new Student() { StudentID = 2, StudentName = "Steve", age = 21 } ,
new Student() { StudentID = 3, StudentName = "Bill", age = 18 } ,
new Student() { StudentID = 4, StudentName = "Ram" , age = 20 } ,
new Student() { StudentID = 5, StudentName = "Ron" , age = 21 }
};
//following converts list into dictionary where StudentId is a key
IDictionary<int, Student> studentDict =
studentList.ToDictionary<Student, int>(s => s.StudentID);
foreach(var key in studentDict.Keys)
Console.WriteLine("Key: {0}, Value: {1}",
key, (studentDict[key] as Student).StudentName);最新文章
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