你不能那样使用它们。他们是事件 - 而不是财产。您需要添加一个事件处理程序。类似于：

You can''t use them like that. They''re events - not properties. You need to add an eventhandler. Something like:

public partial class Form1 : Form
{
    private bool dateChanged = false;

    private void Form1_Load(object sender, EventArgs e)
    {
        dateTimePicker1.ValueChanged += new System.EventHandler(dateTimePicker1_ValueChanged);
    }

    private void dateTimePicker1_ValueChanged(object sender, EventArgs e)
    {
        dateChanged = true;
        //Here you can do stuff that needs to be done when the value changes
    }

    private void button1_Click(object sender, EventArgs e)
    {
        //Example: Here you can check if the value has changed since you opened the form:
        if (dateChanged)
        {
            //The date has been changed - do what I need to do
        }
    }
}