Lambda表达式不适用于过滤列表中的obj

Question

User select month, and dynamically 4 textbox + a button (save row) for each day will be drawn; every textbox has the textbox.Tag = day who refers.

When user click on save row I will it to select only the textboxes of the corresponding row (expecting 4 textboxes).

code that generate the textboxes:

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);

I try this:

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 

Any help is very appreciated ^_^

Answer 1

You are comparing two object directly, and by default this will be done by references comparison.

// 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

You want to compare the value of these date instead:

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();

我已经从Xiaoy312的建议（感谢^^）开始，并在类似的线程上阅读了有关Cast命令的内容，从而创建了此代码。