在逐字字符串文字中替换？

Question

与此相关的问题.有关如何内C#写长长的SQL查询,该解决方案建议,长的SQL查询应该写成:

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
    "; 

这让我对另一个相关问题感到好奇.我能以某种方式使用替代吗？也就是说,如果说表名更改但查询保持不变,我将如何管理？我是否必须回归使用另一种使用字符串连接构建字符串的方法,还是有更优雅的方法？

Answer 1

为什么不使用string.Format？在您给出的具体示例中,您可以执行类似的操作

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

并调用

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

Answer 2

是的,您可以使用String.Format方法.

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_TYPE
FROM
    {0} AS ct INNER JOIN {1} AS c
        ON ct.CUSTOMER_TYPE_ID = c.CUSTOMER_TYPE_ID
"; 

string endQuery = String.Format(query, custtype, cust);

String.Format方法将使用字符串后面的参数顺序替换{x}标识的参数,因此{0}将替换为custtype的值,而{1}将替换为cust的值.