LINQ表达式优化语法？

Question

foreach (var item in mainCanvas.Children)
{
    if (item is Button)
    {
        (item as Button).Content = "this is a button";
    }                
}

我可以使用LINQ或.NET 4的其他功能来更简洁(可能是高性能的)吗？

Answer 1

你可以使用Enumerable.OfType:

foreach (var button in mainCanvas.Children.OfType<Button>())
{
    button.Content = "this is a button";
}

性能测量

方法1:OPs原始建议

foreach (var item in mainCanvas.Children)
{
    if (item is Button)
    {
        (item as Button).Content = "this is a button";
    }                
}

方法2:OfType

foreach (var button in mainCanvas.Children.OfType<Button>())
{
    button.Content = "this is a button";
}

方法3:仅施放一次

foreach (var item in mainCanvas.Children)
{
    Button button = item as Button;
    if (button != null)
    {
        button.Content = "this is a button";
    }                
}

方法4:for循环:

List<object> children = mainCanvas.Children;
for (int i = 0; i < children.Count; ++i)
{
    object item = children[i];
    if (item is Button)
    {
        (item as Button).Content = "this is a button";
    }                
}

结果

Iterations per second

Method 1: 18539180
Method 2:  7376857
Method 3: 19280965
Method 4: 20739241

结论

• 通过使用简单的for循环代替,可以获得最大的改进foreach.
• 通过仅浇铸一次也可以略微提高性能.
• 使用OfType速度相当慢.

但请记住首先优化可读性,并且只有在性能分析的情况下才会优化性能,并发现此特定代码是性能瓶颈.