how to use Double.TryParse in smart device(mobile) in C#

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C#

Hello,
I'm developing a application in Smart Device using C# in that I used Double.TryParse and it is giving error: 'double' does not contain a definition for 'TryParse'. Please send code for this.
My code is:
NOTE: Given that first answer is not working I tried:

private void MapCurrentLocBtn_Click(object sender, EventArgs e)
{
    double lat, lon;
    if (internetConnected && Double.TryParse(currentLatitudeTbx.Text, out lat)
        && Double.TryParse(currentLongitudeTbx.Text, out lon))
}