c# - InvalidOperationException 错误

Question

我正在创建一个方法来处理 DataList 中的删除按钮事件，它正在正确地执行功能，但是我得到了这个异常:

Collection was modified; enumeration operation may not execute.

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. 

Exception Details: System.InvalidOperationException: Collection was modified; enumeration operation may not execute.

这是我的代码:

protected void delete(object sender, CommandEventArgs e) 
        {
            if ((e.CommandName == "delete") && (e.CommandArgument != null))
            {
                foreach (DataListItem item in DataList2.Items)
                {
                    Label post_IDLabel = (Label)item.FindControl("post_IDLabel");
                    string connStr = ConfigurationManager.ConnectionStrings["MyDbConn"].ToString();
                    SqlConnection conn = new SqlConnection(connStr);
                    SqlCommand cmd = new SqlCommand("delete_post", conn);
                    cmd.CommandType = CommandType.StoredProcedure;
                    int post_ID = Convert.ToInt32(post_IDLabel.Text);
                    string email = Session["email"].ToString();
                    int course_ID = Convert.ToInt32(Request.QueryString["courseID"]);
                    cmd.Parameters.Add(new SqlParameter("@course_ID", course_ID));
                    cmd.Parameters.Add(new SqlParameter("@myemail", email));
                    cmd.Parameters.Add(new SqlParameter("@post_ID", post_ID));
                    conn.Open();
                    cmd.ExecuteNonQuery();
                    conn.Close();
                    DataList2.DataBind();
                }
            }

Answer 1

将 DataList2.DataBind(); 从 foreach 循环中取出

            foreach (DataListItem item in DataList2.Items)
            {
                Label post_IDLabel = (Label)item.FindControl("post_IDLabel");
                string connStr = ConfigurationManager.ConnectionStrings["MyDbConn"].ToString();
                SqlConnection conn = new SqlConnection(connStr);
                SqlCommand cmd = new SqlCommand("delete_post", conn);
                cmd.CommandType = CommandType.StoredProcedure;
                int post_ID = Convert.ToInt32(post_IDLabel.Text);
                string email = Session["email"].ToString();
                int course_ID = Convert.ToInt32(Request.QueryString["courseID"]);
                cmd.Parameters.Add(new SqlParameter("@course_ID", course_ID));
                cmd.Parameters.Add(new SqlParameter("@myemail", email));
                cmd.Parameters.Add(new SqlParameter("@post_ID", post_ID));
                conn.Open();
                cmd.ExecuteNonQuery();
                conn.Close();
            }
            DataList2.DataBind();