Display List<String> in textBox (Winforms)

Question

Noob question... I'm trying to display a List in a textbox... unfortunately, my code only displays the first element in the list...

    private void Form1_Load(object sender, EventArgs e)
    {
        List<String> vegetables = new List<String>();
        vegetables.Add("tomato");
        vegetables.Add("carrot");
        vegetables.Add("celery");
        vegetables.Add("potato");

        textBox1.Text = displayMembers(vegetables);
    }

    public string displayMembers(List<String> vegetables)
    {
        foreach (String s in vegetables)
        {
            return s.ToString();
        }
        return null;
    }

How do I get the textBox to display all of the members? Where is my mistake?

Solution 1

Once you return s.ToString(), the rest of that method stops running.
A method cannot return multiple things.

You probably want to write

someTextBox.Text = String.Join(Environment.NewLine, vegetables);

Solution 2

Use string.Join():

textbox1.Text = string.Join(" ", vegetables);

The answer was closer and easier than you thought :)

Note: as mentioned in the comments, this particular function has several overloads added in v4.0 of the .Net framework. If you want to see what is available for earlier versions use the Other Versions dropdown just under the title on the MSDN doco page.

Solution 3

You need to concatenate the strings somehow, like

public string displayMembers(List<String> vegetables)
{
    return string.Join(", ", vegetables.ToArray());
}

or

public string displayMembers(List<String> vegetables)
{
    return string.Join(Environment.NewLine, vegetables.ToArray());
}

Solution 4

You're doing a foreach, but returning at the first element. This is going to cause it to just display the first element.

Instead, you probably want to do something like:

public string DisplayMembers(IEnumerable<String> vegetables)
{
    return String.Join(", ", vegetables);
}

This uses String.Join to "stitch together" the vegetables into a single string, which can then be shown in a TextBox.

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Comments

[Ry-]

Doesn't string.Join only take arrays? You'll need to call ToArray().

[sq33G]

@minitech Welcome to .NET 4.0

[Ry-]

@sq33G: Oh, thanks for pointing that out - I always use .NET 2.0 so I'm not up to date with new features :) (Actually, though, the question doesn't mention the framework version.)