String.Join on a list of objects

Question

In C#, if I have a List<MyObj> where MyObj is a custom class with an overridden ToString() method such that each MyObj object in the List can be easily converted to a string.

How can I join this List<MyObj> with a delimiter, such as for example a pipe (|) into a single string.

So, if I had 3 MyObj objects whose ToString methods would produce AAA, BBB, CCC respectively. I would create a single string: AAA|BBB|CCC.

For a list of a simpler type, such as List<string>, I perform this simply as: String.Join("|", myList.ToArray());. Is there a way I can do something similar to that? Or am I forced to iterate over the Object List and use a StringBuilder to append each object's ToString in the list together?

Related (2008): Join collection of objects into comma-separated string — Peter Mortensen
– Peter Mortensen, Commented Jun 11, 2021 at 2:06

Jon Skeet · Accepted Answer · 2012-05-10 19:06:27Z

67

In .NET 4, you could just use:

var x = string.Join("|", myList);

.NET 3.5 doesn't have as many overloads for string.Join though - you need to perform the string conversion and turn it into an array explicitly:

var x = string.Join("|", myList.Select(x => x.ToString()).ToArray());

Compare the overloads available:

answered May 10, 2012 at 19:06

Jon Skeet

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3 Comments

Ângelo Polotto Over a year ago

Can the LINQ Join replace the string.Join?

Jon Skeet Over a year ago

@ÂngeloPolotto: No, they're completely different operations.

Frijey Labs Over a year ago

Thanks, worked perfectly with: var x = string.Join("|", myList.Select(x => x.myProperty.ToString()).ToArray());

Peter Mortensen · Accepted Answer · 2021-06-11 02:00:42Z

4

Thank you, Jon Skeet. For a more complex object I use the below:

string.Join("-", item.AssessmentIndexViewPoint.Select(x =>
              x.ViewPointItem.Name).ToList())

edited Jun 11, 2021 at 2:00

Peter Mortensen

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answered Feb 25, 2021 at 9:11

Shojaeddin

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