问题描述
我想知道这两种符号之间的区别.
I would like to know the difference between these 2 notations.
首先我有一个存储过程
CREATE PROCEDURE AddSomething( @zonename varchar(50), @desc varchar(255), @TheNewId int OUTPUT ) AS
BEGIN
INSERT INTO a_zone(zonename, descr) VALUES(@zonename, @desc)
SELECT @TheNewId = SCOPE_IDENTITY()
END
如果我以这种方式添加参数有什么区别
What is the difference if I add parameters in this manner
SqlCommand Cmd = new SqlCommand("AddSomething", oConn);
Cmd.CommandType = CommandType.StoredProcedure;
SqlParameter oParam1 = Cmd.Parameters.AddWithValue("@zonename", sName);
SqlParameter oParam2 = Cmd.Parameters.AddWithValue("@desc", description);
和
SqlCommand Cmd2 = new SqlCommand("AddSomething", oConn);
Cmd2.CommandType = CommandType.StoredProcedure;
cmd2.Parameters.Add("@zonename", SqlDbType.VarChar).Value = zonename.Text.Trim();
cmd2.Parameters.Add("@desc", SqlDbType.VarChar).Value = desc.Text.Trim();
推荐答案
以下是一些说明:
Add 和 AddWithValue 命令的区别
Dim cmd as new SqlCommand("SELECT * FROM MyTable WHERE MyDate>@TheDate",conn)
cmd.Parameters.Add("@TheDate",SqlDbType.DateTime).Value="2/1/2007"
对比
cmd.Parameters.AddWithValue("@TheDate","2/1/2007")
Add 强制将字符串转换为日期，因为它进入参数.AddWithValue 会简单地将字符串传递给 SQL Server.
"Add forces the conversion from string to date as it goes into the parameter. AddWithValue would have simply passed the string on to the SQL Server.
当使用 Parameters.Add 时 - SqlDbType 在编译时是已知的
When using
Parameters.Add- the SqlDbType is known at compile time
当使用 Parameters.AddWithValue 时，该方法必须对值进行装箱和拆箱以找出其类型.
When using Parameters.AddWithValue the method has to box and unbox the value to find out its type.
前者的额外好处是 Add 代码更安全并将协助抵御 SQL 注入攻击，代码安全如果您尝试传递与 SqlDb 类型不匹配的值已定义 - 错误将在 .Net 代码中捕获，您将不会有等待往返.
Additional benefits of the former is that Add is a bit more code safe
and will assist against SQL injection attacks , code safe in terms
that if you try to pass a value that doesn't match the SqlDb type
defined - the error will be caught in .Net code and you will not have
to wait for the round trip back.
- http://msdn.microsoft.com/en-us/library/system.data.sqlclient.sqlcommand.parameters.aspx
- http://msdn.microsoft.com/en-us/library/yy6y35y8.aspx
编辑:
获取输出参数的示例:
C#
cmd.Parameters.Add(new SqlParameter("@TheNewId", SqlDbType.Int, int.MaxValue));
cmd.Parameters("@TheNewId").Direction = ParameterDirection.Output;
cmd.ExecuteNonQuery();
int theNewID = (int)cmd.Parameters("@TheNewId").Value;
VB.Net
cmd.Parameters.Add(New SqlParameter("@TheNewId", SqlDbType.Int, Int32.MaxValue))
cmd.Parameters("@TheNewId").Direction = ParameterDirection.Output
cmd.ExecuteNonQuery()
Dim theNewID As Int32 = DirectCast(cmd.Parameters("@TheNewId").Value, Int32)
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