c# - 仅更改月份和年份的 DateTimePicker

Question

UI 应该保持不变我不想这样做:

dateTimePicker1.Format = DateTimePickerFormat.Custom;
dateTimePicker1.CustomFormat = "mm-yyyy";
dateTimePicker1.ShowUpDown = true; 

用户可以选择年份和月份，将 DateTimePicker 更改为 Month/Year 选择器，MonthCalendar 也是如此。
我不想使用第三方控件，但如果它是唯一的答案，我会使用任何免费的月/年选择器控件。

Answer 1

这是一个简单的 DateTimePicker 自定义控件，它预先定义了自定义 DateTime 格式并修改了 MonthCalendar查看，配置它仅显示打开时的月份和年份。
我添加了一个公共(public)属性 ShowToday ，允许指定 MonthCalendar 弹出窗口是否应显示 Today日历界面底部的日期。
自定义控件覆盖 OnDropDown要获取 MonthCalendar 弹出窗口的句柄，请发送 DTM_GETMONTHCAL 消息并更改其当前 View 发送 MCM_SETCURRENTVIEW , 指定 MCMV_YEAR 作为值参数。
这是它的样子:

using System.ComponentModel;
using System.Runtime.InteropServices;
using System.Windows.Forms;

[DesignerCategory("Code")]
class DateTimePickerYearMonth : DateTimePicker
{
    public DateTimePickerYearMonth() {
        this.CustomFormat = "MM-yyyy";
        this.Format = DateTimePickerFormat.Custom;
        this.Value = DateTime.Now;
    }

    [
        Browsable(true), EditorBrowsable(EditorBrowsableState.Always), DefaultValue(false),
        Category("Appearance"), 
        Description("Shows or hides \"Today\" date at the bottom of the Calendar Control")
    ]
    public bool ShowToday {
        get => m_ShowToday;
        set {
            if (value != m_ShowToday) {
                m_ShowToday = value;
                ShowMonCalToday(m_ShowToday);
            }
        }
    }

    protected override void OnHandleCreated(EventArgs e)
    {
        base.OnHandleCreated(e);
        ShowMonCalToday(m_ShowToday);
    }

    protected override void OnDropDown(EventArgs e)
    {
        var hWnd = SendMessage(this.Handle, DTM_GETMONTHCAL, 0, 0);
        if (hWnd != IntPtr.Zero) {
            SendMessage(hWnd, MCM_SETCURRENTVIEW, 0, (int)MonCalView.MCMV_YEAR);
        }
        base.OnDropDown(e);
    }

    private void ShowMonCalToday(bool show)
    {
        int styles = SendMessage(this.Handle, DTM_GETMCSTYLE, 0, 0).ToInt32();
        styles = show ? styles &~(int)MonCalStyles.MCS_NOTODAY : styles | (int)MonCalStyles.MCS_NOTODAY;
        SendMessage(this.Handle, DTM_SETMCSTYLE, 0, styles);
    }
        
    [DllImport("user32.dll")]
    static extern IntPtr SendMessage(IntPtr hWnd, int Msg, int wParam, int lParam);

    private const int DTM_FIRST = 0x1000;
    private const int DTM_GETMONTHCAL = DTM_FIRST + 8;
    private const int DTM_SETMCSTYLE = DTM_FIRST + 11;
    private const int DTM_GETMCSTYLE = DTM_FIRST + 12;
    private const int MCM_FIRST = 0x1000;
    private const int MCM_GETCURRENTVIEW = MCM_FIRST + 22;
    private const int MCM_SETCURRENTVIEW = MCM_FIRST + 32;
    private bool m_ShowToday = false;

    public enum MonCalView : int
    {
        MCMV_MONTH = 0,
        MCMV_YEAR = 1,
        MCMV_DECADE = 2,
        MCMV_CENTURY = 3
    }

    public enum MonCalStyles : int
    {
        MCS_DAYSTATE = 0x0001,
        MCS_MULTISELECT = 0x0002,
        MCS_WEEKNUMBERS = 0x0004,
        MCS_NOTODAYCIRCLE = 0x0008,
        MCS_NOTODAY = 0x0010,
        MCS_NOTRAILINGDATES = 0x0040,
        MCS_SHORTDAYSOFWEEK = 0x0080,
        MCS_NOSELCHANGEONNAV = 0x0100
    }
}