class 方法+C# 使用的实例化引用对象的最佳位置在哪里

Question

我有一个简单而愚蠢的问题，但我希望找到一个答案，让我清楚地了解 C# 引用对象以及实例化它们的最佳位置。我已经在 Class 声明之后声明了 openfile 变量，这样我就可以从 class.every 中的任何其他方法引用它，事情正常，直到我按下添加照片按钮并选择一张照片，如果我确实再次按下按钮并取消了显示对话框 openfile.FileName 不保存文件扩展名。为了解决这个问题，我确实将这行代码 openfile = new OpenFileDialog(); 移到了 class constructor.Is 以这种方式实例化对象是错误的，它将在 RAM.or 实例化仅在您要使用它的地方放置对象。

 private void addPhotoBtn_Click(object sender, RoutedEventArgs e)
        {
            openfile = new OpenFileDialog();
            openfile.Filter = "Images |*.JPG; *.PNG";
            if (openfile.ShowDialog() == true)
            {
                userImage.Source = new BitmapImage(new Uri(openfile.FileName, UriKind.RelativeOrAbsolute));

                filename = openfile.SafeFileName;
                sourcePath = @openfile.FileName;
                targetPath = System.IO.Path.GetDirectoryName(System.IO.Path.GetDirectoryName(System.IO.Directory.GetCurrentDirectory())) + "/Images/users/" + getTime + System.IO.Path.GetExtension(openfile.FileName);
            }
        }
 private void saveUserBtn_Click(object sender, RoutedEventArgs e)
        {


            string fname, lname, username, password, email, phone, address, role, photo = "";
            int spec_id; int dept_id;
            fname = firstNameTextBox.Text.ToString();
            lname = lastNameTextBox.Text.ToString(); ;
            username = usernameTextBox.Text.ToString(); ;
            password = passwordBox.Password;
            email = emailTextBox.Text.ToString(); ;
            phone = phoneTextBox.Text.ToString(); ;
            address = addressTextBox.Text.ToString();
            spec_id = specComboBox.SelectedIndex;
            role = roleComboBox.Text.ToString();

            if (deptComboBox.SelectedIndex >= 0)
                dept_id = int.Parse(deptComboBox.SelectedValue.ToString());
            else
                dept_id = 0;

            // Input Validation
            if (state == "add" && sourcePath != null || sourcePath != null && state != "add")
            {
                photo = new Uri("pack://application:,,/CMMS;component/images/users/") + getTime + System.IO.Path.GetExtension(openfile.FileName);
            }
            .
            .
            .

Answer 1

如果要到处访问文件名，不为空，指定一个本地更改并在选择叔叔时保留地址。在命名空间之后

           private const string FileName = string.Empty;

所以你的代码

        private void addPhotoBtn_Click(object sender, RoutedEventArgs e)
         {
             openfile = new OpenFileDialog();
             openfile.Filter = "Images |*.JPG; *.PNG";
             if (openfile.ShowDialog() == true)
               {
                  userImage.Source = new BitmapImage(new Uri(openfile.FileName, UriKind.RelativeOrAbsolute));

                  filename = openfile.SafeFileName;
                  sourcePath = @openfile.FileName;
                  this.FileName = @openfile.FileName;
                  targetPath = System.IO.Path.GetDirectoryName(System.IO.Path.GetDirectoryName(System.IO.Directory.GetCurrentDirectory())) + "/Images/users/" + getTime + System.IO.Path.GetExtension(openfile.FileName);
                }
           }
         private void saveUserBtn_Click(object sender, RoutedEventArgs e)
         {
           string fname, lname, username, password, email, phone, address, role, photo = "";
           int spec_id; int dept_id;
           fname = firstNameTextBox.Text.ToString();
           lname = lastNameTextBox.Text.ToString(); ;
           username = usernameTextBox.Text.ToString(); ;
           password = passwordBox.Password;
           email = emailTextBox.Text.ToString(); ;
           phone = phoneTextBox.Text.ToString(); ;
           address = addressTextBox.Text.ToString();
           spec_id = specComboBox.SelectedIndex;
           role = roleComboBox.Text.ToString();

           if (deptComboBox.SelectedIndex >= 0)
               dept_id = int.Parse(deptComboBox.SelectedValue.ToString());
           else
                dept_id = 0;

             // Input Validation
          if (state == "add" && sourcePath != null || sourcePath != null && state != "add")
           {
              photo = new Uri("pack://application:,,/CMMS;component/images/users/") + getTime + System.IO.Path.GetExtension(this.FileName);
            }
        .
        .
        .

class 方法+C# 使用的实例化引用对象的最佳位置在哪里

where is the best place to instantiate reference object used by class methods+C#

c#

wpf

openfiledialog