关于一个存储过程执行的问题

要求在存储一个存储过程中实现增，删，该，查的操作，，单一的学生表ALTER proc [dbo].[Students](  @typeint int ,--0,表示添加，1表示更新，2，表示删除，3表示查询  @StudentID int,  @StudentNumber  int,  @StudentName varchar(50),  @StudentSex varchar(10),  @StudentClass varchar(50),  @StudentNianJi varchar(50),  @StudentCS  datetime,  @StudentAdd varchar(50),  @StudentPhone varchar(50),  @StudentBeiZhu text,  @retint int output,  @retval nvarchar(100) output)asdeclare @intranscount int,@blf_alph nvarchar(50),@bsl_brief nvarchar(4000)     set @intranscount=@@trancount if @typeint=0  begin     if exists (select * from  StudenInfo where StudentNumber=@StudentNumber)     set @retval='已经存在名称为['+@StudentNumber+']的学生编号，添加失败！'     set @retint=-1 end  if @intranscount=0 begin transaction    insert into StudenInfo (StudentNumber,StudentName,StudentSex,StudentClass,StudentNianJi,StudentCS,StudentAdd,StudentPhone,StudentBeiZhu)    values(@StudentNumber,@StudentName,@StudentSex,@StudentClass,@StudentNianJi,@StudentCS,@StudentAdd,@StudentPhone,@StudentBeiZhu) if @@error<>0     select @bsl_brief = '向数据库中插入了一行学生编号为['+@StudentNumber+']，学生名称为【'+@StudentNumber+'】的数据，添加成功！'     if @@trancount>@intranscount commit  transaction     set  @retint=1     return 1 --判断更新   if @typeint=1          if not exists(select * from StudenInfo where StudentNumber=@StudentNumber)    set @retval='不存在要更新的学生信息，更新失败!'    set @retint =-1   return -1   --更新的操作      if exists(select * from StudenInfo where StudentNumber<>@StudentNumber and StudentID=@StudentID)    set @retval='已存在名称为['+ @StudentNumber+']的学生编号，更新失败'     set  @retint =-1    return -1    --执行的操作      if exists(select * from StudenInfo where StudentNumber<>@StudentNumber and StudentID<>@StudentID)    select @bsl_brief = '学生编号将由['+StudentNumber+'] 更改为 ['+@StudentNumber+'],更新成功，' from  StudenInfo where StudentNumber=@StudentNumber update StudenInfo set   StudentNumber=@StudentNumber,   StudentName=@StudentNumber,   StudentSex=@StudentSex,   StudentClass=@StudentClass,   StudentNianJi=@StudentNianJi,   StudentCS=@StudentCS,   StudentAdd=@StudentAdd,   StudentPhone=@StudentPhone,   StudentBeiZhu=@StudentBeiZhu   where StudentID=@StudentID   if @@trancount>@intranscount commit  transaction   set  @retint=1   return 1 --执行删除的操作   if @typeint=2  if exists(select * from  StudenInfo where StudentID<>@StudentID)   set @retval='不存在要删除的信息'   set  @retint=-1   return -1   if @intranscount=0 begin transaction   if exists(select * from StudenInfo where StudentID=@StudentID)    select @bsl_brief = '成功删除了编号为['+@StudentID+'],学号为['+@StudentNumber+']的学生信息'   delete  from StudenInfo where    StudentID=@StudentID     if @@trancount>@intranscount commit  transaction     set  @retint=1     return 1 ----执行查询的操作 if @typeint=3  select * from  StudenInfo   if @@trancount>@intranscount commit  transaction  set  @retint=1  return 1 
我在vs中执行的时候我觉得逻辑上是没有我在vs中执行的时候我觉得逻辑上是没有错的，但报错
  SqlConnection conn = new SqlConnection(ConfigurationManager.AppSettings["SQLConnString"].ToString());            conn.Open();            string sql= "Students";            SqlCommand com = new SqlCommand(sql, conn);            com.CommandType = CommandType.StoredProcedure;          
  SqlParameter[] Parameterss = {                                         new SqlParameter("@typeint",SqlDbType.Int),                                         new SqlParameter("@StudentNumber",SqlDbType.Int),                                         new SqlParameter("@StudentName",SqlDbType.VarChar,50),                                         new SqlParameter("@StudentSex",SqlDbType.VarChar,10),                                         new SqlParameter("@StudentClass",SqlDbType.VarChar,50),                                         new SqlParameter("@StudentNianJi",SqlDbType.VarChar,50),                                         new SqlParameter("@StudentCS",SqlDbType.DateTime),                                         new SqlParameter("@StudentAdd",SqlDbType.VarChar,50),                                         new SqlParameter("@StudentPhone",SqlDbType.VarChar,50),                                         new SqlParameter("@StudentBeiZhu",SqlDbType.Text),                                         new SqlParameter("@retint",SqlDbType.Int),                                         new SqlParameter("@retval",SqlDbType.VarChar,100)                                   };            Parameterss[0].Value=0;            Parameterss[1].Value = TextBox1.Text;            Parameterss[2].Value = TextBox2.Text;            Parameterss[3].Value = TextBox3.Text;            Parameterss[4].Value = TextBox4.Text;            Parameterss[5].Value = TextBox5.Text;            Parameterss[6].Value = TextBox6.Text;            Parameterss[7].Value = TextBox7.Text;            Parameterss[8].Value = TextBox8.Text;            Parameterss[9].Value = TextBox9.Text;            Parameterss[10].Direction= ParameterDirection.Output;            Parameterss[11].Direction = ParameterDirection.Output;            com.Parameters.Add(Parameterss[0]);            com.Parameters.Add(Parameterss[1]);            com.Parameters.Add(Parameterss[2]);            com.Parameters.Add(Parameterss[3]);            com.Parameters.Add(Parameterss[4]);            com.Parameters.Add(Parameterss[5]);            com.Parameters.Add(Parameterss[6]);            com.Parameters.Add(Parameterss[7]);            com.Parameters.Add(Parameterss[8]);            com.Parameters.Add(Parameterss[9]);            com.Parameters.Add(Parameterss[10]);            com.Parameters.Add(Parameterss[11]);            com.ExecuteNonQuery();            if (com.ExecuteNonQuery() > 0)            {                if (int.Parse(Parameterss[10].Value.ToString()) > 0)                {                    Response.Write(Parameterss[11].Value.ToString());                    Response.Write("成功");                }                else                {                    Response.Write(Parameterss[11].Value.ToString());                    Response.Write("失败");                }            }            else            {                Response.Write("数据库执行不成");                                    }