Combobox selectedValue在C＃中崩溃ControlBox

Question

当我从我的组合框中分配所选值时，我的Winforms应用程序不会通过controlBox关闭（最小化，最大化工作但不关闭！）

如果我注释掉以下代码，它似乎有效：

    private void Form1_Load(object sender, EventArgs e)
    {
        // TODO: This line of code loads data into the 'dataSet1.NewSelectCommand' table. You can move, or remove it, as needed.
        this.newSelectCommandTableAdapter.Fill(this.dataSet1.NewSelectCommand);

    }

    private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
    {
        string databaseName = string.Empty;
        databaseName = comboBox1.SelectedItem.ToString();
    }

Answer 1

private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
{
    string databaseName = string.Empty;
    if(comboBox1.SelectedItem != null) databaseName = comboBox1.SelectedItem.ToString();
}