How to reduce the following code using C#

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C#

.NET

WinForms

I am using XMLtextreader I want to loop through about 16 times.
So the reader works for 16 times consuming much time How to reduce the above code

int []c=new int[28];
                    for (int b = 0; b < diff.Count; b++)
                    {
                        using (XmlTextReader reader = new XmlTextReader(filename))
                        {
                            bool isInside = false;
                            double x1 = 0; double y1 = 0; double z1 = 0; double x2 = 0; double y2 = 0; double z2 = 0;
                            while (reader.Read())
                            {
                                reader.WhitespaceHandling = WhitespaceHandling.None;
                                
                                if (!isInside && reader.LocalName == "Child" && reader.GetAttribute("id") == diff[b].Key && reader.GetAttribute("type") == lstGivenString[0])
                                {
                                    isInside = true;
                                   c[0]++;
                                }
                                else if (!isInside && reader.LocalName == "Child" && reader.GetAttribute("id") == diff[b].Key && reader.GetAttribute("type") == lstGivenString[1])
                                {
                                    isInside = true;
                                    c[1]++;
                                }
                                else if (!isInside && reader.LocalName == "Child" && reader.GetAttribute("id") == diff[b].Key && reader.GetAttribute("type") == lstGivenString[2])
                                {
                                    isInside = true;
                                   c[2]++;
                                }
}
}
}