101个LINQ例子.docx
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101个LINQ例子
101个LINQ例子
RestrictionOperators
∙Where-Simple1
publicvoidLinq1（）
{
int[]numbers={5,4,1,3,9,8,6,7,2,0};
varlowNums=
fromninnumbers
wheren<5
selectn;
Console.WriteLine（"Numbers<5:
"）;
foreach（varxinlowNums）
{
Console.WriteLine（x）;
}
}
∙Where-Simple2
publicvoidLinq2（）
{
Listproducts=GetProductList（）;
varsoldOutProducts=
frompinproducts
wherep.UnitsInStock==0
selectp;
Console.WriteLine（"Soldoutproducts:
"）;
foreach（varproductinsoldOutProducts）
{
Console.WriteLine（"{0}issoldout!
",product.ProductName）;
}
}
∙Where-Simple3
publicvoidLinq3（）
{
Listproducts=GetProductList（）;
varexpensiveInStockProducts=
frompinproducts
wherep.UnitsInStock>0&&p.UnitPrice>3.00M
selectp;
Console.WriteLine（"In-stockproductsthatcostmorethan3.00:
"）;
foreach（varproductinexpensiveInStockProducts）
{
Console.WriteLine（"{0}isinstockandcostsmorethan3.00.",product.ProductName）;
}
}
∙Where-Drilldown
publicvoidLinq4（）
{
Listcustomers=GetCustomerList（）;
varwaCustomers=
fromcincustomers
wherec.Region=="WA"
selectc;
Console.WriteLine（"CustomersfromWashingtonandtheirorders:
"）;
foreach（varcustomerinwaCustomers）
{
Console.WriteLine（"Customer{0}:
{1}",customer.CustomerID,customer.CompanyName）;
foreach（varorderincustomer.Orders）
{
Console.WriteLine（"Order{0}:
{1}",order.OrderID,order.OrderDate）;
}
}
}
∙Where-Indexed
publicvoidLinq5（）
{
string[]digits={"zero","one","two","three","four","five","six","seven","eight","nine"};
varshortDigits=digits.Where（（digit,index）=>digit.LengthConsole.WriteLine（"Shortdigits:
"）;
foreach（vardinshortDigits）
{
Console.WriteLine（"Theword{0}isshorterthanitsvalue.",d）;
}
}
ProjectionOperators
∙Select-Simple1
publicvoidLinq6（）
{
int[]numbers={5,4,1,3,9,8,6,7,2,0};
varnumsPlusOne=
fromninnumbers
selectn+1;
Console.WriteLine（"Numbers+1:
"）;
foreach（variinnumsPlusOne）
{
Console.WriteLine（i）;
}
}
∙Select-Simple2
publicvoidLinq7（）
{
Listproducts=GetProductList（）;
varproductNames=
frompinproducts
selectp.ProductName;
Console.WriteLine（"ProductNames:
"）;
foreach（varproductNameinproductNames）
{
Console.WriteLine（productName）;
}
}
∙Select-Transformation
publicvoidLinq8（）
{
int[]numbers={5,4,1,3,9,8,6,7,2,0};
string[]strings={"zero","one","two","three","four","five","six","seven","eight","nine"};
vartextNums=
fromninnumbers
selectstrings[n];
Console.WriteLine（"Numberstrings:
"）;
foreach（varsintextNums）
{
Console.WriteLine（s）;
}
}
Select-AnonymousTypes1
publicvoidLinq9（）
{
string[]words={"aPPLE","BlUeBeRrY","cHeRry"};
varupperLowerWords=
fromwinwords
selectnew{Upper=w.ToUpper（）,Lower=w.ToLower（）};
foreach（varulinupperLowerWords）
{
Console.WriteLine（"Uppercase:
{0},Lowercase:
{1}",ul.Upper,ul.Lower）;
}
}
Select-AnonymousTypes2
publicvoidLinq10（）
{
int[]numbers={5,4,1,3,9,8,6,7,2,0};
string[]strings={"zero","one","two","three","four","five","six","seven","eight","nine"};
vardigitOddEvens=
fromninnumbers
selectnew{Digit=strings[n],Even=（n%2==0）};
foreach（vardindigitOddEvens）
{
Console.WriteLine（"Thedigit{0}is{1}.",d.Digit,d.Even?
"even":
"odd"）;
}
}
∙Select-AnonymousTypes3
publicvoidLinq11（）
{
Listproducts=GetProductList（）;
varproductInfos=
frompinproducts
selectnew{p.ProductName,p.Category,Price=p.UnitPrice};
Console.WriteLine（"ProductInfo:
"）;
foreach（varproductInfoinproductInfos）
{
Console.WriteLine（"{0}isinthecategory{1}andcosts{2}perunit.",productInfo.ProductName,productInfo.Category,productInfo.Price）;
}
}
∙Select-Indexed
publicvoidLinq12（）
{
int[]numbers={5,4,1,3,9,8,6,7,2,0};
varnumsInPlace=numbers.Select（（num,index）=>new{Num=num,InPlace=（num==index）}）;
Console.WriteLine（"Number:
In-place?
"）;
foreach（varninnumsInPlace）
{
Console.WriteLine（"{0}:
{1}",n.Num,n.InPlace）;
}
}
∙Select-Filtered
publicvoidLinq13（）
{
int[]numbers={5,4,1,3,9,8,6,7,2,0};
string[]digits={"zero","one","two","three","four","five","six","seven","eight","nine"};
varlowNums=
fromninnumbers
wheren<5
selectdigits[n];
Console.WriteLine（"Numbers<5:
"）;
foreach（varnuminlowNums）
{
Console.WriteLine（num）;
}
}
∙SelectMany-Compoundfrom1
publicvoidLinq14（）
{
int[]numbersA={0,2,4,5,6,8,9};
int[]numbersB={1,3,5,7,8};
varpairs=
fromainnumbersA
frombinnumbersB
whereaselectnew{a,b};
Console.WriteLine（"Pairswherea"）;
foreach（varpairinpairs）{
Console.WriteLine（"{0}islessthan{1}",pair.a,pair.b）;
}
}
∙SelectMany-Compoundfrom2
publicvoidLinq15（）
{
Listcustomers=GetCustomerList（）;
varorders=
fromcincustomers
fromoinc.Orders
whereo.Total<500.00M
selectnew{c.CustomerID,o.OrderID,o.Total};
ObjectDumper.Write（orders）;
}
SelectMany-Compoundfrom3
publicvoidLinq16（）
{
Listcustomers=GetCustomerList（）;
varorders=
fromcincustomers
fromoinc.Orders
whereo.OrderDate>=newDateTime（1998,1,1）
selectnew{c.CustomerID,o.OrderID,o.OrderDate};
ObjectDumper.Write（orders）;
}
SelectMany-fromAssignment
publicvoidLinq17（）
{
Listcustomers=GetCustomerList（）;
varorders=
fromcincustomers
fromoinc.Orders
whereo.Total>=2000.0M
selectnew{c.CustomerID,o.OrderID,o.Total};
ObjectDumper.Write（orders）;
}
SelectMany-Multiplefrom
publicvoidLinq18（）
{
Listcustomers=GetCustomerList（）;
DateTimecutoffDate=newDateTime（1997,1,1）;
varorders=
fromcincustomers
wherec.Region=="WA"
fromoinc.Orders
whereo.OrderDate>=cutoffDate
selectnew{c.CustomerID,o.OrderID};
ObjectDumper.Write（orders）;
}
∙SelectMany-Indexed
publicvoidLinq19（）
{
Listcustomers=GetCustomerList（）;
varcustomerOrders=
customers.SelectMany（
（cust,custIndex）=>
cust.Orders.Select（o=>"Customer#"+（custIndex+1）+
"hasanorderwithOrderID"+o.OrderID））;
ObjectDumper.Write（customerOrders）;
}
PartitioningOperators
∙Take-Simple
publicvoidLinq20（）
{
int[]numbers={5,4,1,3,9,8,6,7,2,0};
varfirst3Numbers=numbers.Take（3）;
Console.WriteLine（"First3numbers:
"）;
foreach（varninfirst3Numbers）
{
Console.WriteLine（n）;
}
}
∙Take-Nested
publicvoidLinq21（）
{
Listcustomers=GetCustomerList（）;
varfirst3WAOrders=（
fromcincustomers
fromoinc.Orders
wherec.Region=="WA"
selectnew{c.CustomerID,o.OrderID,o.OrderDate}）
.Take（3）;
Console.WriteLine（"First3ordersinWA:
"）;
foreach（varorderinfirst3WAOrders）
{
ObjectDumper.Write（order）;
}
}
∙Skip-Simple
publicvoidLinq22（）
{
int[]numbers={5,4,1,3,9,8,6,7,2,0};
varallButFirst4Numbers=numbers.Skip（4）;
Console.WriteLine（"Allbutfirst4numbers:
"）;
foreach（varninallButFirst4Numbers）
{
Console.WriteLine（n）;
}
}
∙Skip-Nested
publicvoidLinq23（）
{
Listcustomers=GetCustomerList（）;
varwaOrders=
fromcincustomers
fromoinc.Orders
wherec.Region=="WA"
selectnew{c.CustomerID,o.OrderID,o.OrderDate};
varallButFirst2Orders=waOrders.Skip
（2）;
Console.WriteLine（"Allbutfirst2ordersinWA:
"）;
foreach（varorderinallButFirst2Orders）
{
ObjectDumper.Write（order）;
}
}
∙TakeWhile-Simple
publicvoidLinq24（）
{
int[]numbers={5,4,1,3,9,8,6,7,2,0};
varfirstNumbersLessThan6=numbers.TakeWhile（n=>n<6）;
Console.WriteLine（"Firstnumberslessthan6:
"）;
foreach（varninfirstNumbersLessThan6）
{
Console.WriteLine（n）;
}
}
∙TakeWhile–Indexed
publicvoidLinq25（）
{
int[]numbers={5,4,1,3,9,8,6,7,2,0};
varfirstSmallNumbers=numbers.TakeWhile（（n,index）=>n>=index）;
Console.WriteLine（"Firstnumbersnotlessthantheirposition:
"）;
foreach（varninfirstSmallNumbers）
{
Console.WriteLine（n）;
}
}
//由3整除的第一个元素从开始的所有元素3,9,8,6,7,2,0
SkipWhile-Simple
publicvoidLinq26（）
{
int[]numbers={5,4,1,3,9,8,6,7,2,0};
varallButFirst3Numbers=numbers.SkipWhile（n=>n%3!
=0）;
Console.WriteLine（"Allelementsstartingfromfirstelementdivisibleby3:
"）;
foreach（varninallButFirst3Numbers）
{
Console.WriteLine（n）;
}
}
∙SkipWhile-Indexed
publicvoidLinq27（）//1,3,9,8,6,7,2,0
{
int[]numbers={5,4,1,3,9,8,6,7,2,0};
varlaterNumbers=numbers.SkipWhile（（n,index）=>n>=index）;
Console.WriteLine（"Allelementsstartingfromfirstelementlessthanitsposition:
"）;
foreach（varninlaterNumbers）
{
Console.WriteLine（n）;
}
}
OrderingOperators
∙OrderBy-Simple1
publicvoidLinq28（）
{
string[]words={"cherry","apple","blueberry"};
varsortedWords=
fromwinwords
orderbyw
selectw;
Console.WriteLine（"Thesortedlistofwords:
"）;
foreach（varwinsortedWords）
{
Console.WriteLine（w）;
}
}
∙OrderBy-Simple2
publicvoidLinq29（）
{
string[]words={"cherry","apple","blueberry"};
varsortedWords=
fromwinwords
orderbyw.Length
selectw;
Console.WriteLine（"Thesortedlistofwords（bylength）:
"）;
foreach（varwinsortedWords）
{
Console.WriteLine（w）;
}
}
∙OrderBy-Simple
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