How to use string.join in method

Scarlett72
Scarlett72 used Ask the Experts™
on
I'm trying to create a method that returns a comma separated list of all Calendar controls on a page, the solutions I've read have suggested using string.join; however, I an confused on how to implement this.  Could this also be an alternative solution?

protected String GetAllCalControls()
    {
        StringBuilder countCal = new StringBuilder();            
        foreach (Control ctrl in Page.Controls)
        {
            foreach (Control childc in ctrl.Controls)
            {
                if (childc is Calendar)
                {
                    countCal.Append(childc.ID+",");
                }
            }
        }
        countCal.Remove(countCal.Length, -1);
        return countCal.ToString();
    }

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Commented:
You might be looking for something like:
private string GetAllControls()
{
	return string.Join(",", (from Control control in Controls where control is Calendar select (control as Calendar).ID).ToArray());
}

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Make sure you add using System.Linq if it is not already there.

-saige-
Commented:
Actually after looking over your initial request, I determined that the above solution won't work because it does not take into account that controls can have child controls.  So I changed the function like such:
private string GetAllControls(Control parent)
{
	// Create a result string to return
	string result = string.Empty;
	// If the parent has a collection of controls and it is greater than 0
	if (parent.Controls.Count > 0)
	{
		// Use string join and enumerate the child controls in the parent collection, find the calendar control and retrieve it's name.
		result = string.Join(",", (from Control child in parent.Controls where child is Calendar select (child as Calendar).ID).ToArray());
		// Enumerate through each child control in the parent and see if the child has a control collection, if so select the child control.
		foreach (Control child in (from Control child in parent.Controls where child.Controls.Count > 0 select child))
		{
			// If our result string is not null or empty, we will join the result of this function recursively with the result string, otherwise, call this function and set result to it's return.
			if (!string.IsNullOrEmpty(result))
				result = string.Join(",", new string[] { result, GetAllControls(child) });
			else
				result += GetAllControls(child);
		}
	}
	// If result is not null or empty and the result ends with a comma, strip it off.
	if (!string.IsNullOrEmpty(result) && result.LastIndexOf(",") == result.Length - 1)
		result = result.Substring(0, result.Length - 1);
	// return the result
	return result;
}

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I added some commenting so that you could see what was happening.

-saige-

Author

Commented:
Thank you it_saige, this is fantastic.  I really need to play with it some more and read up on the concepts you've used to fully understand your solution.

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