Question

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LINQ to append to a StringBuilder from a String[]

Forgive my functional programming noobiness, but is it even possible to use a lamba function to append each string in an array to a StringBuilder object?

Is it possible to turn this code:

// string[] errors = ...
StringBuilder sb = new StringBuilder("<ul>");

foreach (var error in errors)
{
    sb.AppendFormat("<li>{0}</li>", error);
}

sb.AppendLine("</ul");
return sb.ToString();

Into something like this:

// string[] errors = ...
StringBuilder sb = new StringBuilder("<ul>");

//I know this isn't right, I don't care about a return value
errors.All(s => sb.AppendFormat("<li>{0}</li>", s));

sb.AppendLine("</ul");
return sb.ToString();

Thanks for any edification!

Answer 1

I haven’t tested it, but something like the following should work…

return errors.Aggregate(new StringBuilder("<ul>"), (sb,s) => sb.AppendFormat("<li>{0}</li>", s))
             .Append("</ul>");
             .ToString();

Aggregate is an IEnumerable extension method… But I might have the order of agruments wrong. Personally, I do not think this buys you much since it less readable, and is doing a foreach internally anyway.