C# 验证字符串预防不起作用？

我正在尝试转换用户输入的数字，TryParse方法不起作用，我希望如果decimelPlacetxtBox文本中也没有数字，它不会崩溃。从逻辑上讲，它不应该崩溃，因为代码是正确的，但它仍然会崩溃，有人能帮我吗。也许这是我的脑子，但我就是搞不懂

 private void btnConvert_Click(object sender, EventArgs e)
    {

        int decimalPlace = int.Parse(decimelPlacetxtBox.Text);


        if (!double.TryParse(txtboxAmount.Text, out double amount) || !int.TryParse(decimelPlacetxtBox.Text, out int decimalPlaces)) return; // Prevents empty string, validation errorerror
        {
            double userInput = Convert.ToDouble(txtboxAmount.Text);

            // Killogram convertion

            if (comboBoxFrom.SelectedItem.ToString() == "KG" && comboBoxTo.SelectedItem.ToString() == "LB")
            {
                double conver = userInput * 2.20462262185;
                txtBoxResult.Text = "Converted Amount : " + conver.ToString("N" + decimalPlace);
            }

            if (comboBoxFrom.SelectedItem.ToString() == "LB" && comboBoxTo.SelectedItem.ToString() == "KG")
            {
                double conver = userInput / 2.2046;
                txtBoxResult.Text = "Converted Amount : " + conver.ToString("N" + decimalPlace);
            }

            if (comboBoxFrom.SelectedItem.ToString() == "ST" && comboBoxTo.SelectedItem.ToString() == "KG")
            {
                double conver = userInput * 6.35;
                txtBoxResult.Text = "Converted Amount : " + conver.ToString("N" + decimalPlace);
            }

                // Pound convertion

                if (comboBoxFrom.SelectedItem.ToString() == "LB" && comboBoxTo.SelectedItem.ToString() == "ST")
            {
                double conver = userInput / 14;
                txtBoxResult.Text = "Converted Amount : " + conver.ToString("N" + decimalPlace);
            }

            if (comboBoxFrom.SelectedItem.ToString() == "ST" && comboBoxTo.SelectedItem.ToString() == "LB")
            {
                double conver = userInput / 14;
                txtBoxResult.Text = "Converted Amount : " + conver.ToString("N" + decimalPlace);
            }

            if (comboBoxFrom.SelectedItem.ToString() == "LB" && comboBoxTo.SelectedItem.ToString() == "KG")
            {
                double conver = userInput / 2.205;
                txtBoxResult.Text = "Converted Amount : " + conver.ToString("N" + decimalPlace);
            }

            {
                comboBoxFrom.SelectedItem = -1;
            }

            // Stone convertion

            if (comboBoxFrom.SelectedItem.ToString() == "ST" && comboBoxTo.SelectedItem.ToString() == "LB")
            {
                double conver = userInput * 14;
                txtBoxResult.Text = "Converted Amount : " + conver.ToString("N" + decimalPlace);
            }

            if (comboBoxFrom.SelectedItem.ToString() == "LB" && comboBoxTo.SelectedItem.ToString() == "ST")
            {
                double conver = userInput / 14;
                txtBoxResult.Text = "Converted Amount : " + conver.ToString("N" + decimalPlace);
            }

            if (comboBoxFrom.SelectedItem.ToString() == "LB" && comboBoxTo.SelectedItem.ToString() == "KG")
            {
                double conver = userInput / 2.205;
                txtBoxResult.Text = "Converted Amount : " + conver.ToString("N" + decimalPlace);


            }

        }
    }

---

当它崩溃时，是否出现任何错误消息？如果是这样，他们会怎么说？没关系，我修复了它，我移动了int-decimalPlace=int.Parse（decimelPlacetxtBox.Text）；在if语句中插入一行