不使用LINQ查询和操作集合 改进代码

当您不想使用LINQ查询和操作集合时，可以使用传统的循环和条件语句来实现相同的功能。以下是一个示例代码，使用传统的方式来过滤一个字符串列表中的所有空字符串，并将非空字符串转换为大写：

List<string> strList = new List<string> { "hello", "", "world", " ", "C#", " " };
List<string> result = new List<string>();

foreach (string str in strList)
{
    if (!string.IsNullOrWhiteSpace(str))
    {
        result.Add(str.ToUpper());
    }
}

在这个示例代码中，我们使用了foreach循环来遍历字符串列表中的每一个字符串。然后，我们使用条件语句判断字符串是否为空或空格，并将非空字符串转换为大写。最后，我们将非空字符串添加到结果列表中。

这种传统的方式虽然代码量比较大，但可以避免使用LINQ时可能会出现的性能问题和语法难度。

相关问题

不使用LINQ查询和操作集合 改进代码 namespace SandwichCalories { class Program { static void Main(string[] args) { // sandwich ingredients and their associated calories Dictionary<string, int> ingredients = new Dictionary<string, int>() { { "Bread", 66 }, { "Ham", 72 }, { "Bologna", 57 }, { "Chicken", 17 }, { "Corned Beef", 53 }, { "Salami", 40 }, { "Cheese, American", 104 }, { "Cheese, Cheddar", 113 }, { "Cheese, Havarti", 105 }, { "Mayonnaise", 94 }, { "Mustard", 10 }, { "Butter", 102 }, { "Garlic Aioli", 100 }, { "Sriracha", 15 }, { "Dressing, Ranch", 73 }, { "Dressing, 1000 Island", 59 }, { "Lettuce", 5 }, { "Tomato", 4 }, { "Cucumber", 4 }, { "Banana Pepper", 10 }, { "Green Pepper", 3 }, { "Red Onion", 6 }, { "Spinach", 7 }, { "Avocado", 64 } }; // prompt user for calorie range Console.Write("Enter minimum calories: "); int min_calories = int.Parse(Console.ReadLine()); Console.Write("Enter maximum calories: "); int max_calories = int.Parse(Console.ReadLine()); // calculate the minimum and maximum calories for the sandwich int min_sandwich_calories = 2 * ingredients["Bread"] + ingredients.Values.Min() * 2; int max_sandwich_calories = 2 * ingredients["Bread"] + ingredients.Values.Max() * 2; // check if the calorie range is valid if (max_calories < min_sandwich_calories) { Console.WriteLine("Sorry, it is impossible to create a sandwich within the given calorie range."); } else { // create the sandwich List<string> sandwich = new List<string> { "Bread" }; int sandwich_calories = 1 * ingredients["Bread"]; while (sandwich_calories < min_calories) { // add random ingredient string ingredient = ingredients.Keys.ElementAt(new Random().Next(ingredients.Count)); sandwich.Add(ingredient); sandwich_calories += ingredients[ingredient]; } while (sandwich_calories <= max_calories) { // add random ingredient string ingredient = ingredients.Keys.ElementAt(new Random().Next(ingredients.Count)); // check if the ingredient is the same as the previous one if (sandwich.Count >= 3 && ingredient == sandwich[sandwich.Count - 2]) { continue; } sandwich.Add(ingredient); sandwich_calories += ingredients[ingredient]; // check if the sandwich is already at the maximum calorie limit if (sandwich_calories == max_sandwich_calories) { break; } } // add the last slice of bread sandwich.Add("Bread"); // print the sandwich and its total calories Console.WriteLine("Your sandwich: " + string.Join(", ", sandwich)); Console.WriteLine("Total calories: " + sandwich_calories); } } } }

以下是不使用LINQ查询和操作集合改进的代码，这里使用了foreach循环和if条件语句来实现相同的功能：

using System;
using System.Collections.Generic;

namespace SandwichCalories
{
    class Program
    {
        static void Main(string[] args)
        {
            // sandwich ingredients and their associated calories
            Dictionary<string, int> ingredients = new Dictionary<string, int>() {
                { "Bread", 66 },
                { "Ham", 72 },
                { "Bologna", 57 },
                { "Chicken", 17 },
                { "Corned Beef", 53 },
                { "Salami", 40 },
                { "Cheese, American", 104 },
                { "Cheese, Cheddar", 113 },
                { "Cheese, Havarti", 105 },
                { "Mayonnaise", 94 },
                { "Mustard", 10 },
                { "Butter", 102 },
                { "Garlic Aioli", 100 },
                { "Sriracha", 15 },
                { "Dressing, Ranch", 73 },
                { "Dressing, 1000 Island", 59 },
                { "Lettuce", 5 },
                { "Tomato", 4 },
                { "Cucumber", 4 },
                { "Banana Pepper", 10 },
                { "Green Pepper", 3 },
                { "Red Onion", 6 },
                { "Spinach", 7 },
                { "Avocado", 64 }
            };

            // prompt user for calorie range
            Console.Write("Enter minimum calories: ");
            int min_calories = int.Parse(Console.ReadLine());
            Console.Write("Enter maximum calories: ");
            int max_calories = int.Parse(Console.ReadLine());

            // calculate the minimum and maximum calories for the sandwich
            int min_sandwich_calories = 2 * ingredients["Bread"] + GetMinValue(ingredients.Values) * 2;
            int max_sandwich_calories = 2 * ingredients["Bread"] + GetMaxValue(ingredients.Values) * 2;

            // check if the calorie range is valid
            if (max_calories < min_sandwich_calories)
            {
                Console.WriteLine("Sorry, it is impossible to create a sandwich within the given calorie range.");
            }
            else
            {
                // create the sandwich
                List<string> sandwich = new List<string> { "Bread" };
                int sandwich_calories = 1 * ingredients["Bread"];

                while (sandwich_calories < min_calories)
                {
                    // add random ingredient
                    string ingredient = GetRandomIngredient(ingredients);
                    sandwich.Add(ingredient);
                    sandwich_calories += ingredients[ingredient];
                }

                while (sandwich_calories <= max_calories)
                {
                    // add random ingredient
                    string ingredient = GetRandomIngredient(ingredients);

                    // check if the ingredient is the same as the previous one
                    if (sandwich.Count >= 3 && ingredient == sandwich[sandwich.Count - 2])
                    {
                        continue;
                    }

                    sandwich.Add(ingredient);
                    sandwich_calories += ingredients[ingredient];

                    // check if the sandwich is already at the maximum calorie limit
                    if (sandwich_calories == max_sandwich_calories)
                    {
                        break;
                    }
                }

                // add the last slice of bread
                sandwich.Add("Bread");

                // print the sandwich and its total calories
                Console.WriteLine("Your sandwich: " + string.Join(", ", sandwich));
                Console.WriteLine("Total calories: " + sandwich_calories);
            }
        }

        // helper methods
        static int GetMinValue(IEnumerable<int> values)
        {
            int minValue = int.MaxValue;
            foreach (int value in values)
            {
                if (value < minValue)
                {
                    minValue = value;
                }
            }
            return minValue;
        }

        static int GetMaxValue(IEnumerable<int> values)
        {
            int maxValue = int.MinValue;
            foreach (int value in values)
            {
                if (value > maxValue)
                {
                    maxValue = value;
                }
            }
            return maxValue;
        }

        static string GetRandomIngredient(Dictionary<string, int> ingredients)
        {
            int index = new Random().Next(ingredients.Count);
            int i = 0;
            foreach (string key in ingredients.Keys)
            {
                if (i == index)
                {
                    return key;
                }
                i++;
            }
            return null;
        }
    }
}

在这个改进的代码中，我们使用了GetMinValue和GetMaxValue方法来获取字典中值的最小值和最大值，使用GetRandomIngredient方法来获取随机的食材名称。虽然这种方式代码量增加了，但是这种方式可以更好地理解代码的每个步骤，也可以更好地掌控代码的细节。

LINQ 查询集合包括子元素集合

LINQ（Language Integrated Query）是.NET框架中的一种查询技术，它提供了一种统一的查询语法，可以用于查询各种数据源，包括集合、数据库、XML等。在LINQ中，可以使用查询表达式或者方法链的方式来进行查询操作。

要查询集合包括子元素集合，可以使用LINQ的嵌套查询功能。嵌套查询是指在查询表达式或者方法链中嵌套另一个查询，以实现对子元素集合的查询。

下面是一个示例，演示如何使用LINQ查询集合包括子元素集合：

// 假设有一个包含学生信息的类
class Student
{
    public string Name { get; set; }
    public List<string> Courses { get; set; }
}

// 创建学生列表
List<Student> students = new List<Student>
{
    new Student { Name = "Alice", Courses = new List<string> { "Math", "English" } },
    new Student { Name = "Bob", Courses = new List<string> { "Science", "History" } },
    new Student { Name = "Charlie", Courses = new List<string> { "Math", "Physics" } }
};

// 使用LINQ查询学生列表中选修了Math课程的学生
var query = from student in students
            where student.Courses.Contains("Math")
            select student;

// 输出查询结果
foreach (var student in query)
{
    Console.WriteLine(student.Name);
}

在上面的示例中，我们创建了一个包含学生信息的类`Student`，其中`Courses`属性是一个子元素集合，表示学生选修的课程。然后我们创建了一个学生列表`students`，包含了几个学生的信息。

接下来，我们使用LINQ查询语法查询了选修了Math课程的学生，通过`where`子句和`Contains`方法来筛选符合条件的学生。最后，我们通过`foreach`循环输出查询结果。