How to make windows form release/close/dispose image file - c++

Question

MY QUESTION: Is there a way to get a windows form to release an open image without closing the form.
MY PROBLEM: I am working on a windows form in c++. I have a program that allows users to edit .bmp images. The user selects the image they would like to edit from a dataGridView. The images are displayed in an image column in the dataGridView. When I load the image into the dataGridView control, the form opens the image file and prevents any further editing of the image file. The image file cannot be edited even if the dataGridView control is deleted. The form must completely close before it releases the image file.
MY CODE:
namespace EditImageTest {
public ref class Form1 : public System::Windows::Forms::Form {
public: Form1(void) {
// create an image column & dataGridView.
System::Windows::Forms::DataGridViewImageColumn^ c = gcnew System::Windows::Forms::DataGridViewImageColumn();
c->ImageLayout = System::Windows::Forms::DataGridViewImageCellLayout::Zoom;
System::Windows::Forms::DataGridView^ dgv = gcnew System::Windows::Forms::DataGridView();
// add column to dataGridView.
dgv->Columns->Add(c);
// add dataGridView to form.
this->Controls->Add(dgv);
// add .bmp image on desktop to dataGridView.
dgv->Rows>Add(System::Drawing::Image::FromFile("C:\\Users\\User\\Desktop\\1.bmp"));
// the form has now opened the .bmp image file preventing any edits on this file.
// you can not even manualy delete this file now.
// attempt to open the .bmp image for editing.
FILE* f;
fopen_s(&f,"C:\\Users\\User\\Desktop\\1.bmp","w");
if(f) {
// write garbage in the .bmp image.
fwrite("SOME TEXT",sizeof(unsigned char),9,f);
// close the .bmp image.
fclose(f);
}
}
protected: ~Form1() { if (components) { delete components; } }
private: System::ComponentModel::Container ^components;
};
}

Answer 1

The Image class creates a memory-mapped file to map the bitmap's pixel data into memory. That's efficient, it won't take space in the swapfile and if the RAM pages are unmapped then they can always be reloaded from the file. Tends to matter for bitmaps, they can be quite large.
But the MMF does create a lock on the file, it won't be released until you dispose the object with the delete operator. Which of course can't happen until after the window is closed.
You avoid this by making a deep copy of the image, allowing the lock to be released quickly. Do so with the Bitmap(Image^) constructor:
auto img = System::Drawing::Image::FromFile("C:\\Users\\User\\Desktop\\1.bmp"));
dgv->Rows>Add(gcnew Bitmap(img));
delete img;