[Solved] StreamWriter Error: The process cannot access the file because it is being used by another process

getting error while creating file if file is not exist. the error is The process cannot access the file 'c:\\temp\\file1.txt' because it is being used by another process.

i m getting error in else part at line using(streamwriter writer=new streamwriter("c:\\temp\\file1.txt",append:true))

string filename = c:\\temp\\file1.txt;
if (file.exists(filename))
{
    string var1 = "fgg";
    string var2 = "gg";
    string print+= var1;
    print += var2;
    using (StreamWriter writer = new StreamWriter("c:\\temp\\file1.txt", append: true))
    {
        writer.writeline(print);
        writer.close();
    }
}
else
{
    string var1 = "fgg";
    string var2 = "gg";
    string print+= var1;
    print += var2;
    using (StreamWriter writer = new StreamWriter("c:\\temp\\file1.txt", append: true))
    {
        writer.writeline(print);
        writer.close();
    }
}