You can use LINQ to group by the column and check if the count is greater than 1 for value in any row. DataTable dt = new DataTable(); dt.Columns.Add("Example"); dt.Rows.Add(dt.NewRow()[0] = "Test"); dt.Rows.Add(dt.NewRow()[0] = "Test"); //check for duplicates ...
BinaryExpression comparison=Expression.GreaterThan(property, constant);//构建 Lambda 表达式Expression<Func<Person,bool>> lambda = Expression.Lambda<Func<Person,bool>>(comparison, parameter);//编译表达式树并使用Func<Person,bool> func =lambda.Compile();//测试查询条件varpeople =new[] {newPerson { Nam...
varstrings=newList<string>{"apple","banana","grape","orange","kiwi"};varquery=strings.Where(str=>str.Length>3).OrderBy(str=>str.Length).ToList();foreach(varstrinquery){Console.WriteLine(str);} 无论是查询表达式还是方法语法,都是LINQ的两种不同的写法,用于在.NET应用程序中进行数据查询和操作。
Into … Count Count Aggregate … Into … LongCount LongCount Aggregate … Into … Max Max Aggregate … Into … Min Min Aggregate … Into … Sum Sum Distinct Distinct Group By GroupBy Group Join GroupJoin Order By OrderBy Order By … Descending OrderByDescending Order By (with multi...
linq1: Where - Simple 1 This sample uses a filter to find all elements of an array with a value less than 5. //c# static void Linq1() { var numbers = new [] { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 }; var lowNums = numbers.Where(n => n < 5); Console.WriteLine("Number...
The Count operator is another aggregate standard query operator. You can determine how many customers spent more than $25,000 by using the following code: Copy using (Entities entities = new Entities()) { var query = (from c in entities.Customers where c.Orders.Sum( o => o.OrderDetails...
参数是委托类型 System.FuncLinq.Queryable 类中调用相同的方法时(如在 LINQ to SQL 中一样),参数类型为 System.Linq.Expressions.Expression方法语法之间的差异的详细信息,请参阅 LINQ 中的查询语法和方法语法。...80", highScoreCount); // Outputs: 4 scores are greater than 80 } } 示例下面的示例演示...
如果你的数据看起来像下面的列表，你可以按复合键分组，然后取每组中的第一个值。OrderBy是可选的 ...
The Count operator is another aggregate standard query operator. You can determine how many customers spent more than $25,000 by using the following code: using (Entities entities = new Entities()) { var query = (from c in entities.Customers where c.Orders.Sum( o => o.OrderDe...
The Enterprise Library is a set of application blocks created by the Microsoft patterns & practices group. Each application block is a set of classes that help perform a common enterprise development task, such as logging, data access, and exception handling. The Logging...