我已经使用IList创建了一个示例应用程序，其中包含100个元素到100万个项目，以查看Count vs Any哪个是最好的。

Code

class Program
{
    static void Main()
    {

        //Creating List of customers
        IList<Customer> customers = new List<Customer>();
        for (int i = 0; i <= 100; i++)
        {
            Customer customer = new Customer
            {
                CustomerId = i,
                CustomerName = string.Format("Customer{0}", i)
            };
            customers.Add(customer);
        }

        //Measuring time with count
        Stopwatch stopWatch = new Stopwatch();
        stopWatch.Start();
        if (customers.Count > 0)
        {
            Console.WriteLine("Customer list is not empty with count");
        }
        stopWatch.Stop();
        Console.WriteLine("Time consumed with count: {0}", stopWatch.Elapsed);

        //Measuring time with any
        stopWatch.Restart();
        if (customers.Any())
        {
            Console.WriteLine("Customer list is not empty with any");
        }
        stopWatch.Stop();
        Console.WriteLine("Time consumed with count: {0}", stopWatch.Elapsed);
        Console.ReadLine();

    }
}

public class Customer
{
    public int CustomerId { get; set; }
    public string CustomerName { get; set; }
}

结果:

任何都比数好。

你可以做一个简单的测试来弄清楚:

var query = //make any query here
var timeCount = new Stopwatch();
timeCount.Start();
if (query.Count > 0)
{
}
timeCount.Stop();
var testCount = timeCount.Elapsed;

var timeAny = new Stopwatch();
timeAny.Start();
if (query.Any())
{
}
timeAny.Stop();
var testAny = timeAny.Elapsed;

检查testCount和testAny的值。

如果您从具有. length或. count的东西开始(例如ICollection<T>， IList<T>， List<T>，等等)，那么这将是最快的选项，因为它不需要通过Any()所要求的GetEnumerator()/MoveNext()/Dispose()序列来检查非空IEnumerable<T>序列。

对于IEnumerable<T>，则Any()通常会更快，因为它只需要查看一次迭代。但是，请注意Count()的LINQ-to-Objects实现确实检查ICollection<T>(使用.Count作为优化)-因此，如果您的底层数据源直接是一个列表/集合，则不会有很大的区别。不要问我为什么不使用非泛型的ICollection…

当然，如果你已经使用LINQ来过滤它(Where等)，你将有一个基于迭代器块的序列，所以这个ICollection<T>优化是无用的。

通常，对于IEnumerable<T>:坚持使用Any();-p

这取决于数据集有多大，以及您的性能要求是什么?

如果不是很大，就用最易读的形式， 这对我来说是任何，因为它比方程更短更易读。

我已经使用IList创建了一个示例应用程序，其中包含100个元素到100万个项目，以查看Count vs Any哪个是最好的。

Code

class Program
{
    static void Main()
    {

        //Creating List of customers
        IList<Customer> customers = new List<Customer>();
        for (int i = 0; i <= 100; i++)
        {
            Customer customer = new Customer
            {
                CustomerId = i,
                CustomerName = string.Format("Customer{0}", i)
            };
            customers.Add(customer);
        }

        //Measuring time with count
        Stopwatch stopWatch = new Stopwatch();
        stopWatch.Start();
        if (customers.Count > 0)
        {
            Console.WriteLine("Customer list is not empty with count");
        }
        stopWatch.Stop();
        Console.WriteLine("Time consumed with count: {0}", stopWatch.Elapsed);

        //Measuring time with any
        stopWatch.Restart();
        if (customers.Any())
        {
            Console.WriteLine("Customer list is not empty with any");
        }
        stopWatch.Stop();
        Console.WriteLine("Time consumed with count: {0}", stopWatch.Elapsed);
        Console.ReadLine();

    }
}

public class Customer
{
    public int CustomerId { get; set; }
    public string CustomerName { get; set; }
}

结果:

任何都比数好。

编辑:在EF 6.1.1版本中修复。这个答案是不实际的

对于SQL Server和EF4-6, Count()的执行速度比Any()快两倍。

当你运行Table.Any()时，它会生成类似这样的东西(警告:不要伤害大脑试图理解它)

SELECT 
CASE WHEN ( EXISTS (SELECT 
    1 AS [C1]
    FROM [Table] AS [Extent1]
)) THEN cast(1 as bit) WHEN ( NOT EXISTS (SELECT 
    1 AS [C1]
    FROM [Table] AS [Extent2]
)) THEN cast(0 as bit) END AS [C1]
FROM  ( SELECT 1 AS X ) AS [SingleRowTable1]

这需要对符合条件的行进行两次扫描。

我不喜欢写Count() > 0，因为它隐藏了我的意图。我更喜欢使用自定义谓词:

public static class QueryExtensions
{
    public static bool Exists<TSource>(this IQueryable<TSource> source, Expression<Func<TSource, bool>> predicate)
    {
        return source.Count(predicate) > 0;
    }
}