C#_建立mdf失败_存取被拒

原本小弟我在WinCE上使用SqlCeEngine都挺好用的
奈何最近专案需要使用PC
于是我查了一下MSDN
以下是代码

String str;SqlConnection myConn = new SqlConnection("Server=localhost;Integrated security=SSPI;database=master");str = "CREATE DATABASE MyDatabase ON PRIMARY " +"(NAME = MyDatabase_Data, " +"FILENAME = 'C:\\MyDatabaseData.mdf', " +"SIZE = 2MB, MAXSIZE = 10MB, FILEGROWTH = 10%)" +"LOG ON (NAME = MyDatabase_Log, " +"FILENAME = 'C:\\MyDatabaseLog.ldf', " +"SIZE = 1MB, " +"MAXSIZE = 5MB, " +"FILEGROWTH = 10%)";SqlCommand myCommand = new SqlCommand(str, myConn);                try                {                    myConn.Open();                    myCommand.ExecuteNonQuery();                    MessageBox.Show("DataBase is Created Successfully", "MyProgram", MessageBoxButtons.OK, MessageBoxIcon.Information);                }                catch (System.Exception ex)                {                    MessageBox.Show(ex.ToString(), "MyProgram", MessageBoxButtons.OK, MessageBoxIcon.Information);                }                finally                {                    if (myConn.State == ConnectionState.Open)                    {                        myConn.Close();                    }                }

但很不幸的出现
System.Data.SqlClient.SqlException(0x80131904): CREATE FILE于尝试开启或建立实体档案'C:\MyDatabaseData.mdf'时,发现作业系统错误 5(存取被拒。)。
CREATE DATABASE失败。某些列出的档案名称无法建立。请检查相关的错误。

我查过很多相关资料
但都无法得到正确解答
恳请各位大大指点迷津