用LINQ c#构建匿名类型的表达式

Question

我有BinaryTree<Student> deserseriizedstudents和linq查询:

var students = DeserializedStudents.OrderBy(testResult => testResult.Test_Result).
Select(cust => new { name = cust.Name, result = cust.Test_Result });

有人能告诉我如何建立一个表达式，等于这个查询?

Answer 1

对于复杂的表达式，您可以欺骗并查看编译器的操作:

Expression<Func<IEnumerable<Student>, IEnumerable<Student>>> expression = 
  query => query
    .OrderBy(testResult => testResult.Test_Result)
    .Select(cust => new { name = cust.Name, result = cust.Test_Result });

看看调试器中的expression。

顺便说一句，LINQPad在这方面很有帮助。

Answer 2

您可以使用IQueryable接口实现来自动构建基于LinQ的表达式:

var query = DeserializedStudents.AsQueryable()
    .OrderBy(testResult => testResult.Test_Result)
    .Select(cust => new { name = cust.Name, result = cust.Test_Result });
var expression = query.Expression;

Answer 3

像这样?:

var students = from cust in DeserializedStudents
               orderby cust.Test_Result
               select new { name = cust.name, result = cust.Test_Result };