Error when using string.Join

Question

I'am loading a text file and displaying the textfile name in a listbox. And when I click the listbox im saving the path of the file to a variable. This works in another application of mine, but in the new application I get the following error :

Error 8 The best overloaded method match for 'string.Join(string, string[])' has some invalid arguments Error 9 Argument 2: cannot convert from 'System.Collections.Generic.IEnumerable' to 'string[]'

This is the code :

string fileloadpath;

private void FileListbox_SelectedIndexChanged(object sender, EventArgs e)
{
  var selectedItems = FileListbox.SelectedItems.Cast<FileItem>();                   

  var all = string.Join(Environment.NewLine, selectedItems.Select(x => x.Path1));

  fileloadpath = all;
}

Edit : I added ToArray() at the end and that fixed it. Thanks guys.

I have one more error related to this :

When I display the file path in the listbox, instead of the actual file name(test.txt), the text is displayed as : "OpenCV.Form1+FileItem"

Here is the code :

void reciperefresh()
   {
       FileListbox.Items.Clear();

       string[] files = Directory.GetFiles(@"C:\Recipe", "*.txt", 
          SearchOption.AllDirectories);

       foreach (string f in files)
       {
           var fileItem = new FileItem { Title1 = Path.GetFileName(f), 
            Path1 = Path.GetFullPath(f) };
           FileListbox.Items.Add(fileItem);

       }
   }

selectedItems.Select(x => x.Path1) will return an IEnumerable. You need to call .ToArray() on that select — Shwrk
– Shwrk, Commented Apr 6, 2018 at 10:37
Hi, adding ToArray() worked. I have one more query related to the same question. Have updated the main question. — user3177511
– user3177511, Commented Apr 6, 2018 at 10:51
@user3177511 I have updated my answer to address your second issue (which should really be a new question) — Owen Pauling
– Owen Pauling, Commented Apr 6, 2018 at 10:54

Samvel Petrosov · Accepted Answer · 2018-04-06 10:36:55Z

2

Try to replace selectedItems.Select(x => x.Path1) with selectedItems.Select(x => x.Path1).ToArray(). You should pass an array of strings instead of IEnumerable<string>.

answered Apr 6, 2018 at 10:36

Samvel Petrosov

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5 Comments

user3177511 Over a year ago

I have one more query related to this, have updated the question.

Samvel Petrosov Over a year ago

@user3177511 override the ToString() method for your FileItem class. If I remember correctly it will be called automatically and will display in the way you write.

user3177511 Over a year ago

Thank you, both your method as well as @Owen's answer worked.

user3177511 Over a year ago

Hi, There is a new error now, when i click on any item in the list box it says "Unable to cast object of type 'System.String' to type 'FileItem'." File item is public string Title1 { get; set; } and public string File1 { get; set; }

Samvel Petrosov Over a year ago

@user3177511 create new question and describe the problem with it's exception. And add there the Click event handler that you have

Owen Pauling · Accepted Answer · 2018-04-06 10:53:48Z

1

Select returns an IEnumerable but the method requires a string[]. Add ToArray after the Select.

var all = string.Join(Environment.NewLine, selectedItems.Select(x => x.Path1).ToArray());

Re: the additional part to your question (which should really be a new question), you need to change it to:

FileListbox.Items.Add(fileItem.Title1);

Otherwise it is using the Object.ToString() method which you are not overriding. Alternatively override the ToString method in your FileItem class.

edited Apr 6, 2018 at 10:53

answered Apr 6, 2018 at 10:36

Owen Pauling

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3 Comments

user3177511 Over a year ago

Perfect. Thank you very much @Owen

user3177511 Over a year ago

There is a new error now, when i click on any item in the list box it says "Unable to cast object of type 'System.String' to type 'FileItem'." File item is public string Title1 { get; set; } and public string File1 { get; set; }

user3177511 Over a year ago

It seems that this new error is because of using Title1 in FileListbox.Items.Add(fileItem.Title1); If I remove Title1, this new error goes away but the file name is incorrect.

NielsNet · Accepted Answer · 2018-04-06 10:36:52Z

1

You need to pass an Array or Strings instead of the Enumerable that your selectedElements are.

answered Apr 6, 2018 at 10:36

NielsNet

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Comments

CodingNagger · Accepted Answer · 2018-04-06 10:37:00Z

1

The error is that you are trying to use an enumeration of string instead of a string array. Try that:

string.Join(Environment.NewLine, selectedItems.Select(x => x.Path1).ToArray());

answered Apr 6, 2018 at 10:37

CodingNagger

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Comments

ankur goel · Accepted Answer · 2018-04-06 10:41:26Z

0

The error is self explanatory. It is saying to convert it to array of string.

answered Apr 6, 2018 at 10:41

ankur goel

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