CODEWITHSUNDEEP
c#asp.netcontrols
user1663870
user1663870

Reputation: 53

Convert 'Control' to textbox and assign it a value

I am trying to create a form. The form controls names are always going to be the same. However the type of control will change. For example, I have a control named "first_name". When the page is initialized, it retrieves data from a database stating what the type of control (TextBox, DropDownList or CheckBox); Then the form is dynamically created on the page. To keep the viewstate, I created the control in the OnInit method.

protected override void OnInit(EventArgs e)
{
    Control first_name;
    string ControlType = GridView1.Rows[0].Cells[1].Text;
    switch (ControlType)
    {
        case("TextBox"):
            first_name = new Control() as TextBox; first_name.ID = "first_name"; this.Controls.Add(first_name);
            break;
        case("DropDownList"):
            first_name = new Control() as DropDownList; first_name.ID = "first_name"; this.Controls.Add(first_name);
            break;
        case("CheckBox"):
            first_name = new Control() as CheckBox; first_name.ID = "first_name"; this.Controls.Add("first_name");
            break;
    }
}

Then I render the control to the page.

protected override void Render(HtmlTextWriter writer)
{
    writer.Write("first_name: ");
    first_name.RenderControl(writer);
}

Next, I try to assign values to the control. This is where I run into problems. I know that when it's declared globally, it is declared as a control and holds those values.

Is there a way to declare it globally from within a function or to change the type of a control after it's been declared globally?

protected void Page_Load(object sender, EventArgs e)
{
    switch (first_name.GetType().ToString())
    {
        case ("TextBox"):
            first_name.Text = "Your First Name...";
            break;
        case ("DropDownList"):
            first_name.Items.Add("Jason");
            first_name.Items.Add("Kelly");
            first_name.Items.Add("Keira");
            first_name.Items.Add("Sandi");
            first_name.Items.Add("Gary");
            break;
        case ("CheckBox"):
            first_name.Checked = true;
            break;
    }        
}

Please provide a way that I can accomplish this.

Upvotes: 1

Views: 27696

Answers (3)

Matthias Meid
Matthias Meid

Reputation: 12513

You can use Control as the static type, and use another variable in each case:

Control ctrl;
switch(type)
{
  case "TextBox":
    var box = new TextBox();
    box.Text = "...";
    ctrl = box;
    break;
}
Page.Controls.Add(ctrl);

Apparently - looking at the overridden Render method - you're doing a lot of stuff by hand that ASP.NET Web Forms do for you. You can simply add ctrl (or any control) to the Page's Controls collection.

The Page.Render methods renders all elements of the Controls collection, unless you override it.

Upvotes: 0

Knaģis
Knaģis

Reputation: 21475

In your OnInit you should do new TextBox() and not new Control() as TextBox since the second will just return null.

Your Page_Load would be something like this:

if (first_name is TextBox)
    ((TextBox)first_name).Text = "Your First Name...";
else if (first_name is DropDownList)
{
    var drp = (DropDownList)first_name;
    drp.Items.Add();
    // ...
}

Upvotes: 7

Tyler Lee
Tyler Lee

Reputation: 2785

To access the type specific properties, you'll need to cast first_name to the appropriate type within your switch/case statement.

protected void Page_Load(object sender, EventArgs e)
{
    switch (first_name.GetType().ToString())
    {
        case ("TextBox"):
            (first_name as TextBox).Text = "Your First Name...";
            break;
        case ("DropDownList"):
            (first_name as DropDownList).Items.Add("Jason");
            (first_name as DropDownList).Items.Add("Kelly");
            (first_name as DropDownList).Items.Add("Keira");
            (first_name as DropDownList).Items.Add("Sandi");
            (first_name as DropDownList).Items.Add("Gary");
            break;
        case ("CheckBox"):
            (first_name as CheckBox).Checked = true;
            break;
    }        
}

Upvotes: 1

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