What you want is:
tblCustomerInfo.Info LIKE '%' + @SEARCH + '%'
(or edit the parameter value to include the % in the first place).
Otherwise, you are either (first sample) searching for the literal “@SEARCH” (not the arg-value), or you are embedding some extra quotes into the query (second sample).
In some ways, it might be easier to have the TSQL just use LIKE @SEARCH
, and handle it at the caller:
command.Parameters.AddWithValue("@SEARCH","%" + searchString + "%");
Either approach should work.