c# - 奇怪的错误(输入字符串的格式不正确。)

Question

这是我的代码:

namespace Class_Properties {
    public partial class Form1 : Form {
        private string firstHeight1 = "";
        public int firstHeight {
            get {
                        return Convert.ToInt32( firstHeight1 );
            }
        }

        public Form1() {
            InitializeComponent();
        }

        private void button1_Click( object sender, EventArgs e ) {
            firstHeight1 = textBox2.Text;

            Form2 secondForm = new Form2();
            secondForm.Show();
        }
    }
}

然后是另一类:

namespace Class_Properties {
    public partial class Form2 : Form {
        public Form2() {
            InitializeComponent();
            Form1 mainWindow = new Form1();
            this.Height = mainWindow.firstHeight;
        }
    }
}

运行时，键入 200作为 textbox2的值，然后单击 button1，然后Visual Studio说以下异常:

我该怎么办才能解决此错误？

Answer 1

这是失败的原因:

        InitializeComponent();
        Form1 mainWindow = new Form1();
        this.Height = mainWindow.firstHeight;  //<--

不管您对另一个 Form1进行了什么操作，它都不会出现在此代码中，因为它是 firstHeight == string.Empty的新实例，将无法解析。

您必须将现有的Form1发送到Form2:

public Form2(Form1 parent)
{
    this.Height = parent.firstHeight;
}

// called like so from Form1:
var form2 = new Form2(this);

尽管诚然，最好只发送您需要的东西:

public Form2(int desiredHeight)
{
    this.Height = desiredHeight;
}

// called like so from Form1:
var form2 = new Form2(this.firstHeight);