其中是实例化类方法使用的引用对象的最佳位置+；C#

我有一个简单而愚蠢的问题，但我希望找到一个答案，让我的头脑清楚C#reference对象，以及在哪里最好地实例化它们。我在类声明之后声明了

openfile

Varaible，这样我就可以引用类中的任何其他方法。在我按下“添加照片”按钮并选择照片之前，一切都正常。如果我再次按下按钮并取消显示对话框，则

openfile.FileName

不会保存文件扩展名。为了解决这个问题，我移动了这行代码

openfile=newopenfiledialog（）到类构造函数。实例化对象的方式是否错误，因为它将在RAM中保存aspace。或者仅在要使用对象的位置实例化对象

 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);
            }
            .
            .
            .

如果要在任何地方访问文件名而不是为空，请指定一个本地更改，并在选择文件名时保留地址。
后命名空间

           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);
            }
        .
        .
        .

在类构造函数中的addPhoto函数外部实例化openfileDialog，而不是每次按下addPhoto按钮时创建新对象，这是错误的吗？public AddUser（）{InitializeComponent（）；deptComboBox.IsEnabled=false；openfile=new OpenFileDialog（）；}没问题。你可以在构造函数中构建它，并在任何地方使用它，但一定要像我的代码一样创建一个局部变量，然后在构造函数中设置它，如：private OpenFileDialog OpenFileDialog=null；在构造函数写入后：openFileDialog=newopenfiledialog（）；