concatenate in vba code example

Example: vba concatenate string

"1" & "2"    => "12"
"1" + "2"    => "12"
"1" + 2      => 3
1 + "2"      => 3
"a" + 2      => type mismatch
"1" & Null   => "1"
"1" + Null   => Null