C# – Drag and drop to Desktop / Explorer

cdrag and dropexplorernetwpf

Following my scenario.

I got an Application which loads a Filestructure (Folders, Files) from a Database into a WPF ListView. Now I'd like to grab a file from this ListView, drag it over my Desktop (or some open explorer window) and drop it there. Basic Drag and Drop, nothing fancy. This sounds like a "standard" function for a windows application – but google won't help.

So how can I achieve this? Interops?

Thanks

Edit: Thanks for the solution, I still had to do some googling. Here's my complete solution.

Best Answer

DragDrop.DoDragDrop can do this as long as you pass it an appropriate DataObject.

First copy the files somewhere. You can use System.IO.Path.GetTempPath() if you don't have anywhere better.

Next create a string array containing the full paths to the files and do the following:

string[] paths = ...;
DragDrop.DoDragDrop(this, new DataObject(DataFormats.FileDrop, paths),
                    DragDropEffects.Copy);

It is actually possible to do this without pre-copying the files but that gets into some complicated IDataObject interactions, so unless your files are potentially very large and aren't already in the filesystem I would try this method first.

This is the style that Microsoft tends to use in their examples.

It appears that the guidance in this area may have changed, as StyleCop now enforces the use of the C# specific aliases.

C# – the difference between const and readonly in C#

Apart from the apparent difference of

having to declare the value at the time of a definition for a const VS readonly values can be computed dynamically but need to be assigned before the constructor exits.. after that it is frozen.
const's are implicitly static. You use a ClassName.ConstantName notation to access them.

There is a subtle difference. Consider a class defined in AssemblyA.

public class Const_V_Readonly
{
  public const int I_CONST_VALUE = 2;
  public readonly int I_RO_VALUE;
  public Const_V_Readonly()
  {
     I_RO_VALUE = 3;
  }
}

AssemblyB references AssemblyA and uses these values in code. When this is compiled:

in the case of the const value, it is like a find-replace. The value 2 is 'baked into' the AssemblyB's IL. This means that if tomorrow I update I_CONST_VALUE to 20, AssemblyB would still have 2 till I recompile it.
in the case of the readonly value, it is like a ref to a memory location. The value is not baked into AssemblyB's IL. This means that if the memory location is updated, AssemblyB gets the new value without recompilation. So if I_RO_VALUE is updated to 30, you only need to build AssemblyA and all clients do not need to be recompiled.

So if you are confident that the value of the constant won't change, use a const.

public const int CM_IN_A_METER = 100;

But if you have a constant that may change (e.g. w.r.t. precision).. or when in doubt, use a readonly.

public readonly float PI = 3.14;

Update: Aku needs to get a mention because he pointed this out first. Also I need to plug where I learned this: Effective C# - Bill Wagner

Best Answer

Related Solutions

C# – the difference between String and string in C#

This is the style that Microsoft tends to use in their examples.

C# – the difference between const and readonly in C#

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