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problem with custom sort function resetting ItemsSource

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Brian Graves
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Brian Graves asked on 27 May 2010, 01:54 AM
I have the following scenario.  I want to be able to custom sort (by number) a column contains the following:
Value 0-2
Value 2-4
Value 4-6
Value 6-8
Value 8-10
Value 10+

I looked at the following article:
http://www.telerik.com/help/silverlight/gridview-sorting-custom.html

It requires that I reset the ItemsSource.  To do this, I have a custom function (passing ItemsSource, SortPropertyName, and NewSortingState) which grabs the first number it can find inside the property value and sorts accordingly.  It took me a long time to write a custom function that would sort either regular strings or string with numbers in it (like the ones shown above) so I am sharing it with anyone having a similar scenario.  To do this in my custom sorting function, my ItemsSource is set with the value returned from this function:

 

        private object PerformCustomStringSort(List<object> ItemsSource, string columnName, SortingState sortState)
        {
            PropertyInfo colNameProp = ItemsSource.First().GetType().GetProperty(columnName);

            if (colNameProp == null)
                return 0;

            var sorted = from i in ItemsSource select i;
            MyComparer comparer = new MyComparer();
            if (sortState == SortingState.Ascending)
                sorted = sorted.OrderBy(item => NumericHelper.ObtainNumber(colNameProp.GetValue(item, null)), comparer);
            else
                sorted = sorted.OrderByDescending(item => NumericHelper.ObtainNumber(colNameProp.GetValue(item, null)), comparer);
            return sorted.ToList();
        }

Here are the other classes that are used to accomplish this:

    public static class NumericHelper
    {
        public static bool IsNumeric(object expression)
        {
            if (expression == null)
                return false;

            double testDouble;
            if (double.TryParse(expression.ToString(), out testDouble))
                return true;

            bool testBool;
            if (bool.TryParse(expression.ToString(), out testBool))
                return true;

            return false;
        }

        public static object ObtainNumber(object objValue)
        {
            char[] arEntireString = Convert.ToString(objValue).ToCharArray();
            int iStart = -1;
            int iLength = 0;
            int i = 0;

            for (i = 0; i < arEntireString.Length; i++)
            {
                if (NumericHelper.IsNumeric(arEntireString[i]))
                {
                    if (iStart == -1)
                    {
                        if (i > 0 && arEntireString[i - 1] == '-')
                        {
                            iStart = i - 1;
                            iLength += 1;
                        }
                        else
                        {
                            iStart = i;
                        }
                    }
                    iLength += 1;
                }
                else
                {
                    if (iStart > -1)
                    {
                        if (arEntireString[i] == '.') //decimal
                        {
                            iLength += 1;
                        }
                        else
                        {
                            break;
                        }
                    }
                }
            }

            if (iStart > -1 && iLength > 0)
            {
                return (Convert.ToDecimal(Convert.ToString(objValue).Substring(iStart, iLength)));
            }
            else
            {
                return objValue;
            }
        }

    }

    public class MyComparer : IComparer<Object>
    {

        public int Compare(Object valueA, Object valueB)
        {
            if (NumericHelper.IsNumeric(valueA) && NumericHelper.IsNumeric(valueB))
                return int.Parse(Convert.ToString(valueA)).CompareTo(int.Parse(Convert.ToString(valueB)));
            else
                return String.Compare(Convert.ToString(valueA), Convert.ToString(valueB));
        }

    }

 

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Maya
Telerik team
answered on 28 May 2010, 10:50 AM
Hi Brian Graves,

Thank you a lot for sharing this great and useful example. Please, keep up in the same spirit. 
I have updated your Telerik points.

All the best,
Maya
the Telerik team

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Brian Graves
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Maya
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