带有字符串列表的ViewState

本文关键字：ViewState 列表 字符串 | 更新日期: 2023-09-27 18:14:59

我试图保存信息从Gridview页面加载到字符串列表。然后我想把这些信息用电子邮件发送出去。我在网上找过这方面的信息，到目前为止我什么也没找到。我不明白我的ViewState实现是否在错误的地方是错误的或简单的。请帮忙吗?

protected void Page_Load(object sender, EventArgs e)
    {
        if (ViewState["messages"] != null)
        {
            messages = (List<string>)ViewState["messages"];
        }
        if (Page.IsPostBack)
        {
            changeByVendor();
            //mailFunction(messages);
        }
        if (!IsPostBack)
        {
            mailFunction(messages);
        }
    }
protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
    {
        if (e.Row.RowType == DataControlRowType.DataRow)
        {
            if ((GridView1.DataSourceID == "SqlDataSource2" || GridView1.DataSourceID == "SqlDataSource1") && !(e.Row.Cells[11].Text.Equals("&nbsp;")))
            {
                DateTime myDate = Convert.ToDateTime(e.Row.Cells[11].Text);
                if (DateTime.Now > myDate)
                {
                    e.Row.ForeColor = System.Drawing.Color.Red;
                }
                DateTime myDate2 = Convert.ToDateTime(e.Row.Cells[13].Text);
                if (myDate2 > DateTime.Now && myDate2 < DateTime.Now.AddDays(28))
                {
                    e.Row.Cells[13].BackColor = System.Drawing.Color.Yellow;
                    string thisRow = "";
                    for (int i = 0; i < e.Row.Cells.Count; i++)
                    {
                        thisRow = thisRow + e.Row.Cells[i];
                    }
                    messages.Add(thisRow);
                }
            }
            else if (GridView1.DataSourceID == "SqlDataSource4" && !(e.Row.Cells[6].Text.Equals("&nbsp;")))
            {
                DateTime myDate = Convert.ToDateTime(e.Row.Cells[6].Text);
                if (DateTime.Now > myDate)
                {
                    e.Row.ForeColor = System.Drawing.Color.Red;
                }
                DateTime myDate2 = Convert.ToDateTime(e.Row.Cells[7].Text);
                if (myDate2 > DateTime.Now && myDate2 < DateTime.Now.AddDays(28))
                {
                    e.Row.Cells[7].BackColor = System.Drawing.Color.Yellow;
                }
            }
            ViewState["messages"] = messages;
        }
    }

带有字符串列表的ViewState

假设我们有以下示例:

List<string> input = new List<string>();
protected void Page_Load(object sender, EventArgs e)
{
    if (ViewState["messages"] != null)
    {
        input = (List<string>)ViewState["messages"];
    }
}
protected void Button1_Click(object sender, EventArgs e)
{
    List<string> msgs = new List<string>() { "1", "2", "3" };
    ViewState["messages"] = msgs;
}

这当然会在视图状态中存储字符串列表。问题是，当我们触发按钮单击事件时，Page_Load事件将在 Button1_Click事件之前触发，因此，视图状态仍然是空的。这可以通过将代码传入Page_PreRender事件来管理，该事件将在button_click事件之后触发。

  protected void Page_PreRender(object sender, EventArgs e)
  {
    if (ViewState["messages"] != null)
    {
        input = (List<string>)ViewState["messages"];
    }
  }
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