Substitution inside verbatim string literals?

Why not make use of string.Format? In the specific example you gave, you could do something like

string query = @"SELECT    c.CUSTOMER_ID,    COALESCE (c.FIRST_NAME, ''_ + ' ' + COALESCE (c.LAST_NAME, '') AS FULL_NAME    ct.NAME as CUSTOMER_TYPEFROM    {0} AS ct INNER JOIN {1} AS c        ON ct.CUSTOMER_TYPE_ID = c.CUSTOMER_TYPE_ID"; 

And the invoke

string real_query = string.Format(query, tblName1, tblName2);

Yes, you can use the String.Format method.

string custtype = "CT_CUSTOMER_TYPE";string cust = "CUSTOMER"; string query = @"SELECT    c.CUSTOMER_ID,    COALESCE (c.FIRST_NAME, ''_ + ' ' + COALESCE (c.LAST_NAME, '') AS FULL_NAME    ct.NAME as CUSTOMER_TYPEFROM    {0} AS ct INNER JOIN {1} AS c        ON ct.CUSTOMER_TYPE_ID = c.CUSTOMER_TYPE_ID"; string endQuery = String.Format(query, custtype, cust);

The String.Format method will replace the parameters identified by {x} sequentially with the arguments following the string, so {0} will be replaced with the value of custtype, and {1} with the value of cust.

You might consider using LINQ to SQL, if you haven't already.

Answering the actual question, you could use string.Format as the others have mentioned if you're creating the query. If you wish to modify an existing string, try using string.Replace or Regex.Replace as described here. That is:

string query = @"    SELECT        c.CUSTOMER_ID,        COALESCE (c.FIRST_NAME, ''_ + ' ' + COALESCE (c.LAST_NAME, '') AS FULL_NAME        ct.NAME as CUSTOMER_TYPE    FROM        CT_CUSTOMER_TYPE AS ct INNER JOIN CUSTOMER AS c            ON ct.CUSTOMER_TYPE_ID = c.CUSTOMER_TYPE_ID    ";query.Replace("CT_CUSTOMER_TYPE", "NEW_TABLE_NAME");