How do I drag and drop files into an application

Question

I ve seen this done in Borland s Turbo C   environment  but I m not sure how to go about it for a C  application I m working on  Are there best practices or gotchas to look out for

User · Answer

You can implement Drag amp Drop in WinForms and WPF     WinForm  Drag from app window    You should add mousemove event   private void YourElementControl MouseMove object sender  MouseEventArgs e                           if  e Button    MouseButtons Left                              DoDragDrop new DataObject DataFormats FileDrop  new string     PathToFirstFile PathToTheNextOne     DragDropEffects Move                                WinForm  Drag to app window    You should add DragDrop event   private void YourElementControl DragDrop object sender  DragEventArgs e                           foreach  string path in  string   e Data GetData DataFormats FileDrop                                 File Copy path  DirPath   Path GetFileName path                                     Source with full code

User · Answer

Note that for this to work  you also need to set the dragDropEffect within  drawEnter    private void Form1 DragEnter object sender  DragEventArgs e        Console WriteLine  quot DragEnter  quot        e Effect   DragDropEffects Copy     Source  Drag and Drop not working in C  Winforms Application

User · Answer

Yet another gotcha   The framework code that calls the Drag-events swallow all exceptions  You might think your event code is running smoothly  while it is gushing exceptions all over the place  You can t see them because the framework steals them   That s why I always put a try catch in these event handlers  just so I know if they throw any exceptions  I usually put a Debugger Break    in the catch part   Before release  after testing  if everything seems to behave  I remove or replace these with real exception handling

User · Answer

Another common gotcha is thinking you can ignore the Form DragOver  or DragEnter  events  I typically use the Form s DragOver event to set the AllowedEffect  and then a specific control s DragDrop event to handle the dropped data

User · Answer

Some sample code     public partial class Form1   Form       public Form1           InitializeComponent          this AllowDrop   true        this DragEnter    new DragEventHandler Form1 DragEnter         this DragDrop    new DragEventHandler Form1 DragDrop              void Form1 DragEnter object sender  DragEventArgs e          if  e Data GetDataPresent DataFormats FileDrop   e Effect   DragDropEffects Copy             void Form1 DragDrop object sender  DragEventArgs e          string   files    string   e Data GetData DataFormats FileDrop         foreach  string file in files  Console WriteLine file

User · Answer

Yet another gotcha   The framework code that calls the Drag-events swallow all exceptions  You might think your event code is running smoothly  while it is gushing exceptions all over the place  You can t see them because the framework steals them   That s why I always put a try catch in these event handlers  just so I know if they throw any exceptions  I usually put a Debugger Break    in the catch part   Before release  after testing  if everything seems to behave  I remove or replace these with real exception handling

User · Answer

Some sample code     public partial class Form1   Form       public Form1           InitializeComponent          this AllowDrop   true        this DragEnter    new DragEventHandler Form1 DragEnter         this DragDrop    new DragEventHandler Form1 DragDrop              void Form1 DragEnter object sender  DragEventArgs e          if  e Data GetDataPresent DataFormats FileDrop   e Effect   DragDropEffects Copy             void Form1 DragDrop object sender  DragEventArgs e          string   files    string   e Data GetData DataFormats FileDrop         foreach  string file in files  Console WriteLine file

User · Answer

Another common gotcha is thinking you can ignore the Form DragOver  or DragEnter  events  I typically use the Form s DragOver event to set the AllowedEffect  and then a specific control s DragDrop event to handle the dropped data

User · Answer

You need to be aware of a gotcha  Any class that you pass around as the DataObject in the drag drop operation has to be Serializable  So if you try and pass an object  and it is not working  ensure it can be serialized as that is almost certainly the problem  This has caught me out a couple of times

User · Answer

Be aware of windows vista windows 7 security rights - if you are running Visual Studio as administrator  you will not be able to drag files from a non-administrator explorer window into your program when you run it from within visual studio  The drag related events will not even fire  I hope this helps somebody else out there not waste hours of their life

User · Answer

Some sample code     public partial class Form1   Form       public Form1           InitializeComponent          this AllowDrop   true        this DragEnter    new DragEventHandler Form1 DragEnter         this DragDrop    new DragEventHandler Form1 DragDrop              void Form1 DragEnter object sender  DragEventArgs e          if  e Data GetDataPresent DataFormats FileDrop   e Effect   DragDropEffects Copy             void Form1 DragDrop object sender  DragEventArgs e          string   files    string   e Data GetData DataFormats FileDrop         foreach  string file in files  Console WriteLine file

User · Answer

Some sample code     public partial class Form1   Form       public Form1           InitializeComponent          this AllowDrop   true        this DragEnter    new DragEventHandler Form1 DragEnter         this DragDrop    new DragEventHandler Form1 DragDrop              void Form1 DragEnter object sender  DragEventArgs e          if  e Data GetDataPresent DataFormats FileDrop   e Effect   DragDropEffects Copy             void Form1 DragDrop object sender  DragEventArgs e          string   files    string   e Data GetData DataFormats FileDrop         foreach  string file in files  Console WriteLine file

User · Answer

Here is something I used  to drop files and or folders full of files  In my case I was filtering for   dwg files only and chose to include all subfolders   fileList is an IEnumerable or similar In my case was bound to a WPF control      var fileList    IList FileList ItemsSource    See https   stackoverflow com a 19954958 492 for details of that trick   The drop Handler        private void FileList OnDrop object sender  DragEventArgs e          var dropped     string   e Data GetData DataFormats FileDrop        var files   dropped ToList         if   files Any          return       foreach  string drop in dropped        if  Directory Exists drop           files AddRange Directory GetFiles drop     dwg   SearchOption AllDirectories         foreach  string file in files              if   fileList Contains file   amp  amp  file ToLower   EndsWith   dwg            fileList Add file

User · Answer

Here is something I used  to drop files and or folders full of files  In my case I was filtering for   dwg files only and chose to include all subfolders   fileList is an IEnumerable or similar In my case was bound to a WPF control      var fileList    IList FileList ItemsSource    See https   stackoverflow com a 19954958 492 for details of that trick   The drop Handler        private void FileList OnDrop object sender  DragEventArgs e          var dropped     string   e Data GetData DataFormats FileDrop        var files   dropped ToList         if   files Any          return       foreach  string drop in dropped        if  Directory Exists drop           files AddRange Directory GetFiles drop     dwg   SearchOption AllDirectories         foreach  string file in files              if   fileList Contains file   amp  amp  file ToLower   EndsWith   dwg            fileList Add file

User · Answer

Yet another gotcha   The framework code that calls the Drag-events swallow all exceptions  You might think your event code is running smoothly  while it is gushing exceptions all over the place  You can t see them because the framework steals them   That s why I always put a try catch in these event handlers  just so I know if they throw any exceptions  I usually put a Debugger Break    in the catch part   Before release  after testing  if everything seems to behave  I remove or replace these with real exception handling

User · Answer

Another common gotcha is thinking you can ignore the Form DragOver  or DragEnter  events  I typically use the Form s DragOver event to set the AllowedEffect  and then a specific control s DragDrop event to handle the dropped data

User · Answer

The solution of Judah Himango and Hans Passant is available in the Designer  I am currently using VS2015

User · Answer

In Windows Forms  set the control s AllowDrop property  then listen for DragEnter event and DragDrop event   When the DragEnter event fires  set the argument s AllowedEffect to something other than none  e g  e Effect   DragDropEffects Move    When the DragDrop event fires  you ll get a list of strings  Each string is the full path to the file being dropped

User · Answer

The solution of Judah Himango and Hans Passant is available in the Designer  I am currently using VS2015

User · Answer

Be aware of windows vista windows 7 security rights - if you are running Visual Studio as administrator  you will not be able to drag files from a non-administrator explorer window into your program when you run it from within visual studio  The drag related events will not even fire  I hope this helps somebody else out there not waste hours of their life

User · Answer

Another common gotcha is thinking you can ignore the Form DragOver  or DragEnter  events  I typically use the Form s DragOver event to set the AllowedEffect  and then a specific control s DragDrop event to handle the dropped data

User · Answer

In Windows Forms  set the control s AllowDrop property  then listen for DragEnter event and DragDrop event   When the DragEnter event fires  set the argument s AllowedEffect to something other than none  e g  e Effect   DragDropEffects Move    When the DragDrop event fires  you ll get a list of strings  Each string is the full path to the file being dropped

User · Answer

In Windows Forms  set the control s AllowDrop property  then listen for DragEnter event and DragDrop event   When the DragEnter event fires  set the argument s AllowedEffect to something other than none  e g  e Effect   DragDropEffects Move    When the DragDrop event fires  you ll get a list of strings  Each string is the full path to the file being dropped

User · Answer

You need to be aware of a gotcha  Any class that you pass around as the DataObject in the drag drop operation has to be Serializable  So if you try and pass an object  and it is not working  ensure it can be serialized as that is almost certainly the problem  This has caught me out a couple of times

User · Answer

In Windows Forms  set the control s AllowDrop property  then listen for DragEnter event and DragDrop event   When the DragEnter event fires  set the argument s AllowedEffect to something other than none  e g  e Effect   DragDropEffects Move    When the DragDrop event fires  you ll get a list of strings  Each string is the full path to the file being dropped

User · Answer

You need to be aware of a gotcha  Any class that you pass around as the DataObject in the drag drop operation has to be Serializable  So if you try and pass an object  and it is not working  ensure it can be serialized as that is almost certainly the problem  This has caught me out a couple of times

User · Answer

Note that for this to work  you also need to set the dragDropEffect within  drawEnter    private void Form1 DragEnter object sender  DragEventArgs e        Console WriteLine  quot DragEnter  quot        e Effect   DragDropEffects Copy     Source  Drag and Drop not working in C  Winforms Application

User · Answer

You can implement Drag amp Drop in WinForms and WPF     WinForm  Drag from app window    You should add mousemove event   private void YourElementControl MouseMove object sender  MouseEventArgs e                           if  e Button    MouseButtons Left                              DoDragDrop new DataObject DataFormats FileDrop  new string     PathToFirstFile PathToTheNextOne     DragDropEffects Move                                WinForm  Drag to app window    You should add DragDrop event   private void YourElementControl DragDrop object sender  DragEventArgs e                           foreach  string path in  string   e Data GetData DataFormats FileDrop                                 File Copy path  DirPath   Path GetFileName path                                     Source with full code

User · Answer

You need to be aware of a gotcha  Any class that you pass around as the DataObject in the drag drop operation has to be Serializable  So if you try and pass an object  and it is not working  ensure it can be serialized as that is almost certainly the problem  This has caught me out a couple of times

User · Answer

Yet another gotcha   The framework code that calls the Drag-events swallow all exceptions  You might think your event code is running smoothly  while it is gushing exceptions all over the place  You can t see them because the framework steals them   That s why I always put a try catch in these event handlers  just so I know if they throw any exceptions  I usually put a Debugger Break    in the catch part   Before release  after testing  if everything seems to behave  I remove or replace these with real exception handling

[c#] How do I drag and drop files into an application?

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