Lambda表達式不適用於過濾列表中的obj

Question

用戶選擇月份，每天將動態繪制4個文本框+一個按鈕（保存行）； 每個文本框都有文本框。Tag=引用的日期。

當用戶單擊保存行時，我將只選擇相應行的文本框（預期有4個文本框）。

生成文本框的代碼：

foreach (DateTime day in monthDays)
{
    var t1 = new TextBox();
    t1.Location = new Point(Origin.X + 90, Origin.Y + 30 * Ycounter);
    t1.Size = new Size(40, 25);
    t1.MaxLength = 5;
    t1.Tag = day;
    AutoControls.Add(t1);
    Controls.Add(t1);

我嘗試這樣：

private void SaveButton_Click(object sender, EventArgs e)
{
    Button b = (Button)sender;
    DateTime d = (DateTime)b.Tag;

    List<TextBox> t = new List<TextBox>(AutoControls.OfType < TextBox());

    //Autocontrols it's the list with ALL the dynamically generates controls in that form.


    var g = t.Where(x => x.Tag == b.Tag); // expecting 4 textboxes, but returns 0
    var g = t.Where(x => x.Tag == b.Tag).ToList(); // 0
    var g = t.FindAll(x => x.Tag == b.Tag); //returns  0 

任何幫助都非常感謝^ _ ^

Answer 1

您正在直接比較兩個object ，默認情況下，這將通過引用比較來完成。

// this for example will never be true, even if today is 20190613
// because they are 2 different instances
(object)new DateTime(2019, 06, 13) == (object)DateTime.Today

您想比較這些日期的值：

t.Where(x => x.Tag is DateTime date && date == d)

Answer 2

List<Control> RecordData = Controls.Cast<Control>().Where(x => x.Tag is DateTime date && date == d).ToList();

我已經從Xiaoy312的建議（感謝^^）開始，並在類似的線程上閱讀了有關Cast命令的內容，從而創建了此代碼。