小编Mar*_*mes的帖子

我正在做一些关于收益率回归性能的测试,我发现它比正常回报慢.

我测试了值变量(int,double等)和一些引用类型(字符串等)......并且两种情况下的yield return都较慢.为什么要用呢？

看看我的例子:

public class YieldReturnTeste
{
    private static IEnumerable<string> YieldReturnTest(int limite)
    {
        for (int i = 0; i < limite; i++)
        {
            yield return i.ToString();
        }
    }

    private static IEnumerable<string> NormalReturnTest(int limite)
    {
        List<string> listaInteiros = new List<string>();

        for (int i = 0; i < limite; i++)
        {
            listaInteiros.Add(i.ToString());
        }
        return listaInteiros;
    }

    public static void executaTeste()
    {
        Stopwatch stopWatch = new Stopwatch();

        stopWatch.Start();

        List<string> minhaListaYield = YieldReturnTest(2000000).ToList();

        stopWatch.Stop();

        TimeSpan ts = stopWatch.Elapsed;


        string elapsedTime = String.Format("{0:00}:{1:00}:{2:00}.{3:00}",

        ts.Hours, …

检查下面的代码:

class Money
{
    public Money(decimal amount)
    {
        Amount = amount;
    }

    public decimal Amount { get; set; }

    public static implicit operator decimal(Money money)
    {
        return money.Amount;
    }

    public static explicit operator int(Money money)
    {
        return (int)money.Amount;
    }
}

我不明白它在我的代码中会有用,我不能只做一个像这样的方法:

public static int returnIntValueFrom(Money money)
{
    return (int)money.Amount;
}

实施不是更容易和更清楚吗？

我正在编写一个生成DataTable的方法,将数据源作为通用的IEnumerable.如果没有值,我试图在字段上设置默认值,代码如下:

private void createTable<T>(IEnumerable<T> MyCollection, DataTable tabela) 
        {
            Type tipo = typeof(T);

            foreach (var item in tipo.GetFields() )
            {
                tabela.Columns.Add(new DataColumn(item.Name, item.FieldType));
            }

            foreach (Pessoa recordOnEnumerable in ListaPessoa.listaPessoas)
            {
                DataRow linha = tabela.NewRow();

                foreach (FieldInfo itemField in tipo.GetFields())
                {
                    Type typeAux = itemField.GetType();

                    linha[itemField.Name] =
                        itemField.GetValue(recordOnEnumerable) ?? default(typeAux); 

                }
            }
        }

它抛出了这个错误:

找不到类型或命名空间名称'typeAux'(您是否缺少using指令或程序集引用？)

为什么？"Default(Type)"函数不应该返回该类型的默认值吗？

我有一个问题，我从一些数据库图像中收到大量直方图。这些直方图表示为向量 (0...255)，我必须识别并使用双峰直方图。

是否有一个公式可以自动识别哪些直方图是双峰的，哪些不是？由于它们是数字向量，我可以使用编程语言（Java/C#）来处理它。

文献中有没有软件识别双峰直方图的标准？

以下是我正在使用的直方图和格式输入的 3 个示例。每个直方图都是一个具有 256 (0...255) 个位置的向量。

Histogram 1
8029, 41, 82, 177, 135, 255, 315, 591, 949, 456, 499, 688, 446, 733, 712, 1595, 2633, 3945, 6134, 9755, 9236, 11911, 11888, 9450, 13119, 8819, 5991, 4399, 6745, 2017, 3747, 1777, 2946, 1623, 2151, 454, 3015, 3176, 2211, 1080, 391, 580, 750, 473, 10424, 334, 559, 621, 340, 2794, 1094, 5274, 2822, 204, 389, 728, 268, 15, 1060, 58, 113, 2728, 52, 3166, 11, 103, 522, 107, …

查看元数据我发现了这个函数:(在"System.Convert"类中)

    //
    // Summary:
    //     Calling this method always throws System.InvalidCastException.
    //
    // Parameters:
    //   value:
    //     The date and time value to convert.
    //
    // Returns:
    //     This conversion is not supported. No value is returned.
    //
    // Exceptions:
    //   System.InvalidCastException:
    //     This conversion is not supported.
    public static bool ToBoolean(DateTime value);

为什么微软这样做？

这个样本:

public static void createDictionary<T>(IEnumerable<T> myRecords)
            where T: T.ID // Wont Compile
        {
            IDictionary<int, T> dicionario = myRecords.ToDictionary(r => r.ID);


            foreach (var item in dicionario)
            {
                Console.WriteLine("Key = {0}",item.Key);

                Type thisType = item.Value.GetType();

                StringBuilder sb = new StringBuilder();

                foreach (var itemField in thisType.GetProperties())
                {
                    sb.AppendLine(string.Format("{0} = {1}", itemField.Name, itemField.GetValue(item.Value, null)));
                }

                Console.WriteLine(sb);
            }

        }

如何强制传递的类型作为参数有一个名为"ID"的字段？

此代码未编译,它抛出以下错误:

'TestesInterfaces.MyCollection'类型已包含'Current'的定义

但是当我删除模糊方法时,它会不断给出其他错误.

有人可以帮忙吗？

public class MyCollection<T> : IEnumerator<T>
{
    private T[] vector = new T[1000];
    private int actualIndex;

    public void Add(T elemento)
    {
        this.vector[vector.Length] = elemento;
    }

    public bool MoveNext()
    {
        actualIndex++;
        return (vector.Length > actualIndex);
    }

    public void Reset()
    {
        actualIndex = -1;
    }

    void IDisposable.Dispose() { }

    public Object Current
    {
        get
        {
            return Current;
        }
    }


    public T Current
    {
        get
        {
            try
            {
                T element = vector[actualIndex];
                return element;
            }
            catch (IndexOutOfRangeException e)
            {
                throw …

我在Microsoft文档中找到以下内容:

Two objects that are equal return hash codes that are equal. However, the reverse is not true: equal hash codes do not imply object equality, because different (unequal) objects can have identical hash code

我做了自己的测试来理解方法:

public static void HashMetod() 
{
    List<Cliente> listClientTest = new List<Cliente>
    {
        new Cliente { ID = 1, name = "Marcos", Phones = "2222"}
    };

    List<Empresa> CompanyList = new List<Empresa>
    {
        new Empresa { ID = 1, name = "NovaQuimica", Clients = listClientTest },
        new …

"假设以下代码:

public class MultiplasHerancas
{
    static GrandFather grandFather = new GrandFather();
    static Father father = new Father();
    static Child child = new Child();

    public static void Test() 
    {
        grandFather.WhoAreYou();
        father.WhoAreYou();
        child.WhoAreYou();

        GrandFather anotherGrandFather = (GrandFather)child;
        anotherGrandFather.WhoAreYou(); // Writes "I am a child"
    }

}

public class GrandFather
{
    public virtual void WhoAreYou() 
    {
        Console.WriteLine("I am a GrandFather");
    }
}

public class Father: GrandFather
{
    public override void WhoAreYou()
    {
        Console.WriteLine("I am a Father");
    }
}

public class Child : Father …