sql语句参数化模糊查询的问题

1、使用参数化SQL语句进行模糊查找的正确方法：

     //定义sql语句

      string sql = "SELECT StudentID,StudentNO,StudentName FROM Student WHERE StudentName like @StudentName";

      //给参数赋值

     command.Parameters.AddWithValue("@StudentName", txtStudentName.Text+"%");

2.错误做法1：

     //定义sql语句

      string sql = "SELECT StudentID,StudentNO,StudentName FROM Student WHERE StudentName like '@StudentName%'";

      //给参数赋值

     command.Parameters.AddWithValue("@StudentName", txtStudentName.Text);

3.错误做法2：

     //定义sql语句

      string sql = "SELECT StudentID,StudentNO,StudentName FROM Student WHERE StudentName like @StudentName%";

      //给参数赋值

     command.Parameters.AddWithValue("@StudentName", txtStudentName.Text);