converting textlabel to double

I'm trying to convert the text string from a TextBox to a double by pressing a button
I've found on the internet that this is done by:

this->textBox1->text->ToDouble;

Intellisense doesn't show ToDouble...

When building I get an error:

error C2039: 'ToDouble' : is not a member of 'System::String'

private: System::Void button1_Click(System::Object^ sender, System::EventArgs^ e) {
this->textBox1->Text-ToDouble
}

How do I convert the string do a double?

Wrong forum.