How to join from an array, after converting each element?

Question

C++ / C#

I have the following loop

r = "";
foreach( var t in arr )
r += "text=" + t + ",";

But as a result, an extra semicolon is formed at the end.
If there was no addition with "text=", then it would suit me. How can I catch the last element or make a join on the converted array? Of course, you can write at the end or there
String.Join( "text=", arr );
r = r.SubString( 0, r.Length-1 );

for( int i = 0; i < arr.Length; i++ )
r += "text" + t + (i == arr.Length-1 ? "" : "," );

But it's kind of long.

Answer 1

string[] arr = new[] { "1", "2" };
var result = string.Join(",", arr.Select(v => $"text={v}"));