如何在動態創建的ASP.net控件中動態創建ASP.net控件

Question

我正在用ASP.net制作應用程序。 我有一個按鈕，單擊后會生成一些html，一些asp文本框和一個asp按鈕（第二個按鈕）。 據我所知，這工作正常。 現在我想要的是，當我單擊第二個新創建的按鈕時，我希望它創建一些html + asp.net文本框。

這讓我感到困惑，有沒有更簡單的方法？ 我似乎無法弄清楚，我為按鈕2創建了onclick事件，但它尚不存在。

非常感謝。

認為以防萬一，您想看一下代碼可能會容易一些，以防萬一。

namespace ConnorMackayWebForm
{
public partial class InspectionCreate : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        //Set the initial amount of areas and hazards
        int areaCount = 0;
        int hazardCount = 0;

        //Check if the viewstate with the area count already exists
        if (ViewState["areaCount"] != null)
        {
            //Convert the view state back to an int
            areaCount = Convert.ToInt32(ViewState["areaCount"]);
        }
        else
        {
            ViewState["areaCount"] = areaCount;
        }

        //Check if the viewstate with the hazard count already exists
        if (ViewState["hazardCount"] != null)
        {
            //Convert the view state back to an int
            hazardCount = Convert.ToInt32(ViewState["hazardCount"]);
        }
        else
        {
            ViewState["hazardCount"] = hazardCount;
        }

        //Create the required number of areas
        for (int i = 1; i <= areaCount; i++)
        {
            createArea(i);
        }

        //Create the required number of hazards
        for (int i = 1; i <= hazardCount; i++)
        {
            createHazard(i);
        }
    }

    protected void btnCreateArea_Click(object sender, EventArgs e)
    {
        //Get the current number of areas
        int areaCount = Convert.ToInt32(ViewState["areaCount"]) + 1;

        //Create the area
        createArea(areaCount);

        //Set the new area into the viewstate
        ViewState["areaCount"] = areaCount;
    }

    protected void btnCreateHazard_Click(object sender, CommandEventArgs areaCount)
    {
        //Get the current number of areas
        int hazardCount = Convert.ToInt32(ViewState["hazardCount"]) + 1;

        //Get the argument from the button
        int placeholderID = Convert.ToInt32(areaCount.CommandArgument);

        //Create the hazard
        createHazard(hazardCount, placeholderID);

        //Set the new hazard into the viewstate
        ViewState["hazardCount"] = hazardCount;
    }

    private void createArea(int areaCount)
    {   
        //Start generating the HTML
        pnlArea.Controls.Add(new LiteralControl("<div class='box'>"));
        pnlArea.Controls.Add(new LiteralControl("<div class='box-header with-border'>"));
        pnlArea.Controls.Add(new LiteralControl("<h2 class='box-title'>Area / Equipment Inspected 1: "));

        //Create the title dropdown
        DropDownList ddArea = new DropDownList();
        ddArea.ID = "ddArea" + areaCount;

        pnlArea.Controls.Add(ddArea);

        //Create the Other textbox in the title
        pnlArea.Controls.Add(new LiteralControl(" Other: "));

        TextBox txtOther = new TextBox();
        txtOther.ID = "txtOther" + areaCount;

        pnlArea.Controls.Add(txtOther);

        //Generate HTML for the box body and begining of first column
        pnlArea.Controls.Add(new LiteralControl("<div class='box-tools pull-right'>"));
        pnlArea.Controls.Add(new LiteralControl("</div>"));
        pnlArea.Controls.Add(new LiteralControl("</div>"));
        pnlArea.Controls.Add(new LiteralControl("<div class='box-body'>"));

        //Placeholder to put future hazards into
        PlaceHolder phHazard = new PlaceHolder();
        phHazard.ID = "phHazard" + areaCount;

        pnlArea.Controls.Add(phHazard);

        //Create hazard button
        pnlArea.Controls.Add(new LiteralControl("<br>"));

        Button btnCreateHazard = new Button();
        //btnCreateHazard.Click += btnCreateHazard_Click;
        btnCreateHazard.ID = "btnCreateHazard" + areaCount;
        btnCreateHazard.Text = "Create Hazard";
        btnCreateHazard.CssClass = "form-control";

        //Pass along the current area count, allowing the onclick to pick it up, pass it to 
        //the create hazard method.  That method will then take the argument and search for a place
        //holder with matching ID and assign the controls to that placeholder.
        btnCreateHazard.Command += btnCreateHazard_Click;
        btnCreateHazard.CommandArgument = areaCount.ToString();

        pnlArea.Controls.Add(btnCreateHazard);

        pnlArea.Controls.Add(new LiteralControl("</div>"));
        pnlArea.Controls.Add(new LiteralControl("</div>"));
    }

    private void createHazard (int hazardCount, int placeholderID)
    {
        //The starting of the HTML rows, etc
        FindControl("phHazard" + placeholderID).Controls.Add(new LiteralControl("<div class='row'>"));
        FindControl("phHazard" + placeholderID).Controls.Add(new LiteralControl("<div class='col-lg-3'>"));
        FindControl("phHazard" + placeholderID).Controls.Add(new LiteralControl("Hazard: "));

        //Create the Hazard Dropdown
        DropDownList ddHazard = new DropDownList();
        ddHazard.ID = "ddHazard" + hazardCount;

        FindControl("phHazard" + placeholderID).Controls.Add(ddHazard);

        //HTML ending the first column, starting second
        FindControl("phHazard" + placeholderID).Controls.Add(new LiteralControl("</div>"));
        FindControl("phHazard" + placeholderID).Controls.Add(new LiteralControl("<div class='col-lg-3'>"));
        FindControl("phHazard" + placeholderID).Controls.Add(new LiteralControl("Hazard Description: "));

        //Create the hazard description textbox
        TextBox txtHazardDesc = new TextBox();
        txtHazardDesc.ID = "txtHazardDesc" + hazardCount;

        FindControl("phHazard" + placeholderID).Controls.Add(txtHazardDesc);

        //HTML ending second column, starting third
        FindControl("phHazard" + placeholderID).Controls.Add(new LiteralControl("</div>"));
        FindControl("phHazard" + placeholderID).Controls.Add(new LiteralControl("<div class='col-lg-3'>"));
        FindControl("phHazard" + placeholderID).Controls.Add(new LiteralControl("Corrective Action Due Date: "));

        //Create the due date textbox
        TextBox txtDueDate = new TextBox();
        txtDueDate.ID = "txtDueDate" + hazardCount;

        FindControl("phHazard" + placeholderID).Controls.Add(txtDueDate);

        //HTML ending the third column, starting fourth
        FindControl("phHazard" + placeholderID).Controls.Add(new LiteralControl("</div>"));
        FindControl("phHazard" + placeholderID).Controls.Add(new LiteralControl("<div class='col-lg-3'>"));
        FindControl("phHazard" + placeholderID).Controls.Add(new LiteralControl("Corrective Action Description: "));

        //Create the corrective action description text box
        TextBox txtActionDesc = new TextBox();
        txtActionDesc.ID = "txtActionDesc" + hazardCount;

        FindControl("phHazard" + placeholderID).Controls.Add(txtActionDesc);

        //End the row
        FindControl("phHazard" + placeholderID).Controls.Add(new LiteralControl("<br>"));
    }
}

}

Answer 1

這是向頁面連續添加按鈕的示例。 每個新創建的按鈕也可以向頁面添加另一個按鈕。 可以與所有類型的控件一起使用。 另外，您還必須在每個PostBack上重新創建動態控件，否則它們及其內容將丟失。

protected void Page_Load(object sender, EventArgs e)
{
    //set the initial number of buttons
    int buttonCount = 1;

    //check if the viewstate with the buttoncount already exists (= postback)
    if (ViewState["buttonCount"] != null)
    {
        //convert the viewstate back to an integer
        buttonCount = Convert.ToInt32(ViewState["buttonCount"]);
    }
    else
    {
        ViewState["buttonCount"] = buttonCount;
    }

    //create the required number of buttons
    for (int i = 1; i <= buttonCount; i++)
    {
        createButton(i);
    }
}

private void createButton(int cnt)
{
    //create a new button control
    Button button = new Button();
    button.Text = "Add another Button (" + cnt + ")";

    //add the correct method to the button
    button.Click += DynamicButton_Click;

    //another control, in this case a literal
    Literal literal = new Literal();
    literal.Text = "<br>";

    //add the button and literal to the placeholder
    PlaceHolder1.Controls.Add(button);
    PlaceHolder1.Controls.Add(literal);
}

protected void DynamicButton_Click(object sender, EventArgs e)
{
    //get the current number of buttons
    int buttonCount = Convert.ToInt32(ViewState["buttonCount"]) + 1;

    //create another button
    createButton(buttonCount);

    //set the new button count into the viewstate
    ViewState["buttonCount"] = buttonCount;
}

更新

您還可以將Command委派給按鈕而不是Click ，並可以將變量和按鈕一起作為CommandArgument 。 您將不得不稍微更改按鈕的創建。

//add the correct method to the button
button.Command += DynamicButton_Command;

//now you can also add an argument to the button
button.CommandArgument = "Create Hazard";

您還需要其他方法來處理按鈕單擊。

protected void DynamicButton_Command(object sender, CommandEventArgs e)
{
    //get the current number of buttons
    int buttonCount = Convert.ToInt32(ViewState["buttonCount"]) + 1;

    //create another button
    createButton(buttonCount);

    //set the new button count into the viewstate
    ViewState["buttonCount"] = buttonCount;

    //get the commandargument from the button
    string buttonArgument = e.CommandArgument.ToString();
}