1 if (AccessCon.ExecuteSql(sql = "select * from salesData where index ='" + man.Index + "'") > 0)
 2             {
 3                 retValue = AccessCon.ExecuteSql(sql = "update salesData set sellingPrize='" + man.SellingPrize + "' where index='" + man.Index + "'");
 4                 Console.WriteLine(sql);
 5             }
 6             else
 7             {
 8                 retValue = AccessCon.ExecuteSql(sql = "insert into salesData values ('" + man.Index + "','" + man.SellingPrize + "')");
 9                 Console.WriteLine(sql);
10             }
11 
12             return retValue;

　　本来想通过select * from salesData where index =' man.Index '执行后的返回值是否大于0判断表中是否已有数据

因为msdn中说返回受影响的行数：

Executes a Transact-SQL statement against the connection and returns the number of rows affected.

但是却没看到备注里说

For UPDATE, INSERT, and DELETE statements, the return value is the number of rows affected by the command. When a trigger exists on a table being inserted or updated, the return value includes the number of rows affected by both the insert or update operation and the number of rows affected by the trigger or triggers. For all other types of statements, the return value is -1. If a rollback occurs, the return value is also -1.

对于UPDATE, INSERT,和 DELETE返回受影响的函数，但是对于所有其他类型的语句，返回值为 -1。如果发生回滚，返回值也为 -1。这样对于search语句来说就不适合ExecuteNonQuery()方法了。