Sorting Generic.List Items

Great example of sorting a Generic.List collection of objects can be found here. For future reference for myself, here is a class that can be reused in future projects whenever I need to sort a collection of custom objects:

///

/// The generic comparer class allows for sorting on a generic collections property fields
/// 

/// An object
public class GenericComparer : IComparer
{
    ///

    /// Creates a new instance of the GenericComparer class
    /// 

    ///
A string expression of the field to sort
    ///
A SortDirection value to indicate     /// Ascending or Descending sort
    public GenericComparer(string sortExpression, SortDirection sortDirection)
    {
        this.SortExpression = sortExpression;
        this.SortDirection = sortDirection;
    }

    ///

    /// Private container for the Sort Direction
    /// 

    private SortDirection sortDirection;

    ///

    /// Private container for the expression used for the sort
    /// 

    private string sortExpression;

    ///

    /// The expression to use during the sort (in this case, the Generic objects field name)
    /// 

    public string SortExpression
    {
        get { return sortExpression; }
        set { sortExpression = value; }
    }

    ///

    /// The direction to perform the sort
    /// 

    public SortDirection SortDirection
    {
        get { return this.sortDirection; }
        set { this.sortDirection = value; }
    }

    ///

    /// Performs the sort on the supplied objects
    /// 

    /// 
    /// The following example shows how to implement and use this class:
    ///  items = MyDataObject.GetObjects();
    ///             items.Sort(new GenericComparer(SortExpression, SortDirection));
    ///         }
    ///     }
    /// ]]>
    /// 
    ///
The first object
    ///
The second object
    /// An int value that specifies the result of the comparison
    public int Compare(T x, T y)
    {
        PropertyInfo propertyInfo = typeof(T).GetProperty(SortExpression);
        IComparable obj1 = (IComparable)propertyInfo.GetValue(x, null);
        IComparable obj2 = (IComparable)propertyInfo.GetValue(y, null);

        if (SortDirection == SortDirection.Ascending)
            return obj1.CompareTo(obj2);
        else
            return obj2.CompareTo(obj1);
    }
}

Wayne  (531 Posts)

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