How to get controls on page in master detail page?

Question

I have master page and its content page. I want to get the textboxes situated on Content page. How can I get them in C# code behind of Content page?

Answer 1

Access it by using it's ID:

Markup:

<asp:TextBox runat="server" ID="myTextBox"></asp:TextBox>

Code behind:

myTextBox.Text = "This is a text!";

Note that you need to add runat="server" for it to be accessible.

Edit
After your comment I think I understand where you're getting at. You'll need to traverse through all controls down the control tree to find all TextBoxes.

Here is a recursive implementation:

public List<Control> FindControls(Control root, Type type)
{
    var controls = new List<Control>();

    foreach (Control ctrl in root.Controls)
    {
        if (ctrl.GetType() == type)
            controls.Add(ctrl);

        if (ctrl.Controls.Count > 0)
            controls.AddRange(FindControls(ctrl, type));
    }

    return controls;
}

To get all TextBoxes in a page you'll call it with Page as root Control:

var allTextBoxes = FindControls(Page, typeof(TextBox));

The above example is to clarify the idea of how you should proceed. I'd do it a bit differently by using an Extension Method:

public static class ExtensionMethods
{
    public static IEnumerable<Control> FindControls(this Control root)
    {
        foreach (Control ctrl in root.Controls)
        {
            yield return ctrl;
            foreach (Control desc in ctrl.FindControls())
                yield return desc;
        }

    }
}

Now you can use it directly on any control and even apply Linq on the result since it's an IEnumerable.

This will get you an array of all controls in a page:

var allControls = this.FindControls().ToArray();

To get an array of all TextBox controls:

var allTextBoxes = this.FindControls()
                       .OfType<TextBox>().ToLArray<TextBox>();

and to get a list of TextBoxes with a specific id:

var myTextBox = this.FindControls()
                    .OfType<TextBox>()
                    .Where<TextBox>(tb => tb.ID.Equals("textBox1")).ToList<TextBox>();

You can also use it in foreach statements:

foreach (Control c in this.FindControls())
{
  ...
}