WPF 学习笔记（五）

一、不可空数据类型 int DateTime boolean

            string str1 = "";
            string s1 = null;

            MessageBox.Show(str1.Length.ToString());
            //MessageBox.Show(s1.Length.ToString()); //空指针会引发异常

            int? i1 = null;
            int i2 = 6;
            i1 = i2;

            int? i3 = null;    //error
            //int i4 = i3;
            int i4 = (int)i3;  //ok,但是如果传入的是NULL类型，会引发异常

　　

二、常用控件

1、PasswordBox  属性password，设置默认密码

        <PasswordBox Password="123" Height="23" HorizontalAlignment="Left" Margin="88,39,0,0" Name="psw" VerticalAlignment="Top" Width="120" />

2、checkbox 属性IsChecked  默认返回boolean? 可空数据类型，因此可以用 == true方法解决是比较好的

        private void checkBox1_Checked(object sender, RoutedEventArgs e)
        {
            if (checkBox1.IsChecked == true)
            {
                MessageBox.Show("确认过眼神");
            }
        }

3、RadioButton  GroupName属性 组的名称

<RadioButton GroupName="Name" Content="RadioButton" Height="16" HorizontalAlignment="Left" Margin="111,122,0,0" Name="radioButton1" VerticalAlignment="Top" />
<RadioButton GroupName="Name" Content="RadioButton" Height="16" HorizontalAlignment="Left" Margin="111,144,0,0" Name="radioButton2" VerticalAlignment="Top" />
<RadioButton GroupName="Name" Content="RadioButton" Height="16" HorizontalAlignment="Left" Margin="111,166,0,0" Name="radioButton3" VerticalAlignment="Top" />
<RadioButton GroupName="age" Content="RadioButton" Height="16" HorizontalAlignment="Left" Margin="269,131,0,0" Name="radioButton4" VerticalAlignment="Top" />
<RadioButton GroupName="age" Content="RadioButton" Height="16" HorizontalAlignment="Left" Margin="269,153,0,0" Name="radioButton5" VerticalAlignment="Top" />

4、datePicker 控件 SelectedDate 赋予时间，获取时间

        private void button1_Click(object sender, RoutedEventArgs e)
        {
            // 取值
            DateTime? value = datePicker1.SelectedDate;
            if (value == null)
            {
                MessageBox.Show("请选择日期");
            }
            else
            {
                MessageBox.Show(value.ToString());
            }
        }

        private void button2_Click(object sender, RoutedEventArgs e)
        {
            datePicker1.SelectedDate = DateTime.Today;

            MessageBox.Show(DateTime.Today.ToString()); // today 属性只包含年月日
            MessageBox.Show(DateTime.Now.ToString());
        }

5、ProgressBar  控件 属性Maximum、Minimum、Value、IsIndeterminate（用于不可控因素）

 <ProgressBar Maximum="100" Minimum="0" Value="10" Height="10" HorizontalAlignment="Left" Margin="24,197,0,0" Name="progressBar1" VerticalAlignment="Top" Width="100" />
 <ProgressBar IsIndeterminate="True" Height="10" HorizontalAlignment="Left" Margin="174,197,0,0" Name="progressBar2" VerticalAlignment="Top" Width="100" />
 <Button Content="加血" Height="23" HorizontalAlignment="Left" Margin="24,213,0,0" Name="button3" VerticalAlignment="Top" Width="75" Click="button3_Click" />
   

        private void button3_Click(object sender, RoutedEventArgs e)
        {
            progressBar1.Value += 5;
        }