How to improve my double.Parse property in usercontrol

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C#

WinForms

user-controls

I have the following code on a UserControl, consisting of a single textbox.

public double txt
{
    get { return double.Parse(txtInputSmall.Text); }
    set { txtInputSmall.Text = value.ToString(); }
}

public string text
{
    get { return txtInputSmall.Text; }
    set { txtInputSmall.Text = value; }
}

I want something that handles the double.Parse for me, like here, so that I don't need to do it for every UserControl I add to my WinForm. The problem is, when my I'm in design view of my WinForm, I keep getting the following message:

Code generation for property 'txt' failed. Error was: 'Property accessor 'txt' on object 'inputcontrolSmall12' threw the following exception: "Input string was not in a correct format"

I think the designer expects the string in the textbox to be a double, which is not, because it's empty. How can I improve this piece of code?