函数改变了代入参数的值,是怎么做到的呢
public static DataSet Query(string SQLString, params SqlParameter[] cmdParms)
{
using (SqlConnection connection = new SqlConnection(factorychoice()))
{
SqlCommand cmd = new SqlCommand();
PrepareCommand(cmd, connection, null, SQLString, cmdParms);
using (SqlDataAdapter da = new SqlDataAdapter(cmd))
{
DataSet ds = new DataSet();
try
{
da.Fill(ds, "ds");
cmd.Parameters.Clear();
}
catch (System.Data.SqlClient.SqlException ex)
{
throw new Exception(ex.Message);
}
return ds;
}
}
}
以上的代码高人所写,我所纳闷的是下面这几句代码
SqlCommand cmd = new SqlCommand();
PrepareCommand(cmd, connection, null, SQLString, cmdParms);
cmd的值经过PrepareCommand函数后,里面的参数改变了,这是为什么呢, PrepareCommand函数如下
private static void PrepareCommand(SqlCommand cmd, SqlConnection conn, SqlTransaction trans, string cmdText, SqlParameter[] cmdParms)
{
if (conn.State != ConnectionState.Open)
conn.Open();
cmd.Connection = conn;
cmd.CommandText = cmdText;
if (trans != null)
cmd.Transaction = trans;
cmd.CommandType = CommandType.Text;//cmdType;
if (cmdParms != null)
{
foreach (SqlParameter parameter in cmdParms)
{
if ((parameter.Direction == ParameterDirection.InputOutput || parameter.Direction == ParameterDirection.Input) &&
(parameter.Value == null))
{
parameter.Value = DBNull.Value;
}
cmd.Parameters.Add(parameter);
}
}
}

我用控制台模拟了一下,并未改变,代码如下
class Program
{
static void Main(string[] args)
{
int i = 3;
addvale(i);
Console.Write(i.ToString());
Console.ReadKey();
}
public static void addvale(int ii)
{
ii = ii + 5;
}
}
高人帮忙解答一下,谢谢.

[解决办法]
需要改传入参数，前边需要加ref
举个例子

C# code

class Program    {        static void Main(string[] args)        {            StringBuilder builder = new StringBuilder();            builder.Append("1111");            StringBuilder builder2 = builder;            Change1(builder);            Console.WriteLine("Change1");            Console.WriteLine(object.ReferenceEquals(builder,builder2).ToString());            Console.WriteLine(builder.ToString());            Console.WriteLine(builder2.ToString());            Change2(ref builder);            Console.WriteLine("Change2");            Console.WriteLine(object.ReferenceEquals(builder, builder2).ToString());            Console.WriteLine(builder.ToString());            Console.WriteLine(builder2.ToString());            Console.ReadKey();        }        static void Change1(StringBuilder builder)        {            builder = new StringBuilder();            builder.Append("2222");        }        static void Change2(ref StringBuilder builder)        {            builder = new StringBuilder();            builder.Append("2222");        }    } 
 
[解决办法]
因为cmd是引用类型。（字符串例外）
[解决办法]
下面那个函数本身就是修改cmd属性的，cmd能不变吗。。。。