FileDialog filter - LINQ concatenation

Question

While creating service to display OpenFileDialog/SaveFileDialog, I was thinking about creating LINQ query/clear C# code to Concatinate()/Join() filter expression.

Do the filter based on this call:

string res = "";
if(new Service().ShowOpenFileDialog(out res,
      new string[]{ "JPG", "TXT", "FBX"},
      new string[]{ "Images", "TextFile", "FilmBox"}))
    Console.WriteLine(res); //DisplayResult

Example definition:

public bool ShowOpenFileDialog(out string result, string[] ext, string[] desc)
{
    if(ext.Length != desc.Length) return false;

    OpenFileDialog diag = new OpenFileDialog();

    // problematic part
    // diag.Filter = "Text File (*.txt)|*.txt";
    // diag.Filter = desc[0] + " (*." + ext[0] + ")|*." + ext[0];
    // diag.Filter += "|"+desc[1] + " (*." + ext[1] + ")|*." + ext[1];

    // I tried something like:
    // diag.Filter = String.Join("|", desc.Concat(" (*." + ext[0] + ")|*." + ext[0]));
    // but not sure how to pass indexes across LINQ queries

    diag.Filter = /* LINQ? */

    if(diag.ShowDialog() == true)
    {
        result = diag.FileName;
        return true;
    }
    return false;
}

Question: Is it possible to create LINQ to concatenate/join 2 arrays in such format? Is it needed to do it by code? If so, what is the cleanest/least expensive solution?

Note: As a filter (result) example:

"Images (*.JPG)|*.JPG |TextFile (*.TXT)|*.TXT |FilmBox (*.FBX)|*.FBX"

EDIT: Also please consider there might be n items in the arrays.

score 3 · Accepted Answer · edited Feb 27 '17 at 15:05

3

You should use Select to iterate over your collection. Also, string interpolation comes in handy here.

string filter = string.Join
                       ( "|"
                       , ext.Zip
                             ( desc
                             , (e, d) => new
                                         { Ext = e
                                         , Desc = d
                                         }
                             )
                            .Select(item => $"{item.Desc} (*.{item.Ext})|*.{item.Ext}")
                       );

edited Feb 27 '17 at 15:05

Tatranskymedved

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answered Feb 27 '17 at 14:52

Patrick Hofman

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Thanks for answer, however if I put this 1to1 in the code, output is: `(*.I)|*.m| (*.T)|*.e| (*.F)|*.i` – Tatranskymedved Feb 27 '17 at 14:56
Not sure what I was thinking, but the updated answer should be better. – Patrick Hofman Feb 27 '17 at 15:01
Indeed it is, but not clear result yet. =) , fixed via edit. – Tatranskymedved Feb 27 '17 at 15:04
Ah, bad copy/pasting from my side. – Patrick Hofman Feb 27 '17 at 15:06
Thanks for the answer, you've really expanded my knowledge (borders) about `Zip`/`Select` - I had no clue I can use it this way! – Tatranskymedved Feb 27 '17 at 15:12

FileDialog filter - LINQ concatenation

1 Answers1