How to auto increment xml file version

I have an xml file which i want to increment the version number each time the user click btnNewfile. it must start from 1000 and increment to by 1. I am also confused on which version must increment or both. the problem is the format when i try to debug. how can i increment it?

xml

<resheader name="version">
<value>2.0</value>
</resheader>

what i have done

     private void btnNewfile_Click(object sender, EventArgs e)
    {

        int current = 1000;
        current++;
        var versionNumber = doc.Descendants("value").FirstOrDefault();
        current = (int)versionNumber;
        versionNumber.SetValue(current + 1); //error here;Input string was not in a correct format.
        lbl_Output_Version.Text = versionNumber.ToString();
    }

the problem comes here as i have these two

<resheader name="resmimetype">text/microsoft-resx</resheader>
<resheader name="version">2.0</resheader> // i only want to update this one

when i debug it is getting the first one with "text/microsoft-resx" and it throws error after that.