使用LINQ查找Winforms的控件？

Question

我试图通过名称找到一种优雅的方式来获取Windows窗体表单上的控件.例如:

MyForm.GetControl "MyTextBox"

...

但这必须确保它递归地通过所有控件.

使用LINQ实现此方法的最优雅方法是什么？

Answer 1

"优雅"控制滤波器(无LINQ)

感谢C#3,有许多优雅的解决方案.这个不使用LINQ查询运算符; 它使用lambdas和delegates.

这会过滤给定条件的所有控件(可以根据多个条件进行筛选).返回多个匹配项.它允许不仅仅是名称检测.

    /// <summary>
    /// Recurses through all controls, starting at given control,
    /// and returns an array of those matching the given criteria.
    /// </summary>

    public Control[] FilterControls(Control start, Func<Control, bool> isMatch) {
        var matches = new List<Control>();

        Action<Control> filter = null;
        (filter = new Action<Control>(c => {
            if (isMatch(c))
                matches.Add(c);
            foreach (Control c2 in c.Controls)
                filter(c2);
        }))(start);

        return matches.ToArray();
    }

过滤器使用...

就使用而言,它非常灵活

Control[] foundControls = null;

// Find control with Name="tabs1".
foundControls = FilterControls(this,
    c => c.Name != null && c.Name.Equals("tabs1"));

// Find all controls that start with ID="panel*...
foundControls = FilterControls(this,
    c => c.Name != null && c.Name.StartsWith("panel"));

// Find all Tab Pages in this form.
foundControls = FilterControls(this,
    c => c is TabPage);

Console.Write(foundControls.Length); // is an empty array if no matches found.

等效扩展方法

扩展方法也为应用程序添加了优雅的继承人.

可以将完全相同的逻辑注入到这样的扩展方法中.

static public class ControlExtensions {

    static public Control[] FilterControls(this Control start, Func<Control, bool> isMatch) {
        // Put same logic here as seen above (copy & paste)
    }
}

扩展用法是:

// Find control with Name="tabs1" in the Panel.
panel1.FilterControls(c => c.Name != null && c.Name.Equals("tabs1"));

// Find all panels in this form
this.FilterControls(c => c is Panel);

返回一个控件的另一个扩展 null

调用第一个扩展方法(参见上文)以获取所有匹配的控件,然后返回匹配中的第一个,否则如果匹配列表为空则返回null.

这是无效的,因为它甚至在找到第一场比赛后迭代所有控件 - 但只是为了SO评论而在这里玩.

    static public Control FilterControlsOne(this Control start, Func<Control, bool> isMatch) {
        Control[] arrMatches = ControlExtensions.FilterControls(start, isMatch);
        return arrMatches.Length == 0 ? null : arrMatches[0];
    }

Answer 2

LINQ不一定最适合未知深度递归; 只需使用常规代码......

public static Control FindControl(this Control root, string name) {
    if(root == null) throw new ArgumentNullException("root");
    foreach(Control child in root.Controls) {
        if(child.Name == name) return child;
        Control found = FindControl(child, name);
        if(found != null) return found;
    }
    return null;
}

有:

Control c = myForm.GetControl("MyTextBox");

或者,如果您不喜欢上面的递归:

public Control FindControl(Control root, string name) {
    if (root == null) throw new ArgumentNullException("root");
    var stack = new Stack<Control>();
    stack.Push(root);
    while (stack.Count > 0) {
        Control item = stack.Pop();
        if (item.Name == name) return item;
        foreach (Control child in item.Controls) {
            stack.Push(child);
        }
    }
    return null;
}

Answer 3

我不认为你可以直接创建递归linq查询,但你可以使用linq创建一个递归方法:

public IEnumerable<Control> FlattenHierarchy(this Control c)
{
    return new[] { c }.Concat(c.Controls.Cast<Control>().SelectMany(child => child.FlattenHierarchy()));
}

这应返回包含控件层次结构中包含的每个控件的序列.然后找到匹配很简单:

public Control FindInHierarchy(this Control control, string controlName)
{
    return control.FlattenHierarchy().FirstOrDefault(c => c.Name == controlName);
}

就个人而言,我会以这种方式避免使用linq.