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我已经创建了动态控件，但是在通过动态控件插入数据时出现错误。下面是我尝试过但无法修复的代码。您的合作将不胜感激。

   public int NumberOfControls
{
    get
    {
        if (ViewState["Count"] == null)
        {
            return 0;
        }
        return (int)ViewState["Count"];
    }
    set
    {
        ViewState["Count"] = value++;
    }
}

private void CreateTextBoxes()
{
    for (int counter = 0; counter <= NumberOfControls; counter++)
    {
        DropDownList ddl = new DropDownList();
        ddl.Width = 150;
        ddl.Height = 18;
        ddl.ID = "Ddl_Item" + (counter + 1).ToString();
        dvContainer.Controls.Add(ddl);
        string sql = "select * from INV.GOODS_MASTER";
        SqlDataAdapter adp = new SqlDataAdapter(sql,cc);
        DataTable dt=new DataTable();
        adp.Fill(dt);
        if (dt.Rows.Count > 0)
        {
            ddl.Items.Clear();
            ddl.DataSource = dt;
            ddl.DataTextField = "GM_NAME";
            ddl.DataValueField = "GM_ID";
            ddl.DataBind();
            ddl.Items.Insert(0, new ListItem("---Select---", string.Empty));
        }

        TextBox tb = new TextBox();
        tb.Width = 150;
        tb.Height = 18;
        tb.TextMode = TextBoxMode.SingleLine;
        tb.ID = "Txt_Quantits" + (counter + 1).ToString();
        // add some dummy data to textboxes
        tb.Text = "Enter Title " + counter;
        dvContainer.Controls.Add(tb);
        //phTextBoxes.Controls.Add(new LiteralControl("<br/>"));


        DropDownList ddl1 = new DropDownList();
        ddl1.Width = 150;
        ddl1.Height = 18;
        ddl1.ID = "Ddl_Unit" + (counter + 1).ToString();
        dvContainer.Controls.Add(ddl1);
        string sql1 = "select * from INV.UNITMASTER";
        SqlDataAdapter adp1 = new SqlDataAdapter(sql1, cc);
        DataTable dt1 = new DataTable();
        adp1.Fill(dt1);
        if (dt1.Rows.Count > 0)
        {
            ddl1.Items.Clear();
            ddl1.DataSource = dt1;
            ddl1.DataTextField = "UM_UNITNAME";
            ddl1.DataValueField = "UM_ID";
            ddl1.DataBind();
            ddl1.Items.Insert(0, new ListItem("---Select---", string.Empty));
        }

        TextBox tb1 = new TextBox();
        tb1.Width = 150;
        tb1.Height = 18;
        tb1.TextMode = TextBoxMode.SingleLine;
        tb1.ID = "Txt_Availabl" + (counter + 1).ToString();
        // add some dummy data to textboxes
        tb.Text = "Enter Title " + counter;
        dvContainer.Controls.Add(tb1);
        //phTextBoxes.Controls.Add(new LiteralControl("<br/>"));
    }
}

private void ReadTextBoxes()
{
    strValue = string.Empty;

    int n = NumberOfControls;

    for (int i = 0; i <= NumberOfControls; i++)
    {
        string boxName = "Ddl_Item" + (i + 1).ToString();
        DropDownList ddl = dvContainer.FindControl(boxName) as DropDownList;
        strValue += ddl.Text + "\n";

        string boxName1 = "Txt_Quantits" + (i + 1).ToString();
        TextBox tb = dvContainer.FindControl(boxName1) as TextBox;
        strValue += tb.Text + "\n";

        string boxName2 = "Ddl_Unit" + (i + 1).ToString();
        DropDownList ddl2 = dvContainer.FindControl(boxName2) as DropDownList;
        strValue += ddl2.Text + "\n";

        string boxName3 = "Txt_Availabl" + (i + 1).ToString();
        TextBox tb1 = dvContainer.FindControl(boxName3) as TextBox;
        strValue += tb1.Text + "\n";
    }
    Response.Write(strValue);
}

protected override void CreateChildControls()
{
    // Here we are recreating controls to persist the ViewState on every post back
    if (Page.IsPostBack)
    {
        //NumberOfControls += 1;
        CreateTextBoxes();
    }
    else
    {
        CreateTextBoxes();
        // Increase the control value to 1
        NumberOfControls = 0;
    }
}

protected void Button1_Click(object sender, EventArgs e)
{
    NumberOfControls += 1;
    //CreateTextBoxes();
}

private void StockEntryBind(string mode)
{
    string sql = "[INV].[SP_StockEntry]";
    SqlCommand cmd = new SqlCommand(sql, cc);
    cmd.Parameters.AddWithValue("@StockEntryId", HiddenField1.Value);
    cmd.Parameters.AddWithValue("@Date", DateTime.Parse(txt_date.Text));
    cmd.Parameters.AddWithValue("@Time", txt_time.Text);
    cmd.Parameters.AddWithValue("@Godown", Ddl_Godown.SelectedItem.Text);

   //Error coming below
    DropDownList ddl = new DropDownList();
    ddl.ID = "Ddl_Item";
    cmd.Parameters.AddWithValue("@Item", ddl.SelectedItem.Text);

    TextBox tb = new TextBox();
    tb.ID = "Txt_Quantits";
    cmd.Parameters.AddWithValue("@Quantity", tb.Text);

    DropDownList ddl1 = new DropDownList();
    ddl1.ID = "Ddl_Unit";
    cmd.Parameters.AddWithValue("@Unit", ddl1.SelectedItem.Text);

    TextBox tb1 = new TextBox();
    tb1.ID = "Txt_Availabl";
    cmd.Parameters.AddWithValue("@AvailableStock", tb1.Text);

    cmd.Parameters.AddWithValue("@mode", mode);
    cmd.CommandType = CommandType.StoredProcedure;
    cmd.ExecuteNonQuery();
}
protected void Button2_Click(object sender, EventArgs e)
{
    StockEntryBind("Insert");
    string jScript = @"javascript: alert('Data has been Inserted successfully');";
    ScriptManager.RegisterClientScriptBlock(Page, Page.GetType(), "clientScript", jScript, true);
}

它没有找到动态控件 ID 来保存数据并显示对象引用未设置为对象的错误。

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1 回答 1

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如果您正在创建动态控件，则需要确保在回发时重新创建它们。这需要在连接视图状态和事件之前完成。创建控件的最佳位置是在 Page_Init 函数期间，而不是 Page_Load。

查看ASP.Net 页面生命周期以了解页面是如何构建的。

于 2013-08-23T13:20:04.557 回答