Hi Raghu,
Based on my understanding, you want to sort a ArrayList which contains some custom objects. The custom object has two properties: FirstName and LastName. Please feel free to tell me if I misunderstood you.
To sort an ArrayList, we can call the Sort method and pass a parameter of type IComparer. In this way, the root issue is how to pass a parameter of type IComparer. We need to create a new class which implements IComparer to change the default compare behavior and make the comparing result as what we want.
The code snippet below shows how to create a general comparer class to compare custom objects.
Custom comparer class:
public class MyComparable<T> : Comparer<T>
{
//The list contains the property names need to be compared.
private List<string> _sortProperties = new List<string>();
public List<string> SortProperties { get { return _sortProperties; } }
//If the sort type is ascending or descending
private bool _isAsc = true;
public bool IsAsc { set { _isAsc = value; } get { return _isAsc; } }
public override int Compare(T x, T y)
{
int compareResult = 0;
if (x != null && y != null)
{
foreach (string pName in _sortProperties)
{
PropertyInfo pInfo = typeof(T).GetProperty(pName);
if (pInfo != null)
{
//Get values of the property.
//The value of X.
object xVal = pInfo.GetValue(x, null);
//The value of Y.
object yVal = pInfo.GetValue(y, null);
//Compare the values.
compareResult = CompareValue(xVal, yVal, pInfo);
//If the the values are not equal, return; otherwise, continue comparing.
if (compareResult != 0)
break;
}
}
}
return compareResult;
}
private int CompareValue(object xVal, object yVal, PropertyInfo p)
{
int res = 0;
if (p != null)
{
Type pType = p.PropertyType;
bool xHasVal = true;
bool yHasVal = true;
//Check if the property is nullable and get its value.
if (pType.IsGenericType && (pType.GetGenericTypeDefinition() == typeof(Nullable<>)))
{
//Check if the nullable object has value.
xHasVal = (bool)(pType.GetProperty("HasValue").GetValue(xVal, null));
yHasVal = (bool)(pType.GetProperty("HasValue").GetValue(yVal, null));
//If it has value, get the value.
if (xHasVal)
xVal = pType.GetProperty("Value").GetValue(xVal, null);
else
xVal = null;
if (yHasVal)
yVal = pType.GetProperty("Value").GetValue(yVal, null);
else
yVal = null;
pType = pType.GetGenericArguments()[0];//Get the true value type of nullable type.
}
if (xHasVal && yHasVal)
{
foreach (Type pInterface in pType.GetInterfaces())
{
if (pInterface == typeof(IComparable))
{
//Call CompareTo method of IComparable.
res = (xVal as IComparable).CompareTo(yVal as IComparable);
break;//Ciomparing finished.
}
else if (pInterface.IsGenericType && (pInterface.GetGenericTypeDefinition() == typeof(IComparable<>)))
{
//Call CompareTo method of Compare<T>
Type paramType = pInterface.GetGenericArguments()[0];//type of T
MethodInfo compareMethod = pInterface.GetMethod("CompareTo", new Type[] { paramType });//Get method
//Execute the method.
res = (int)(compareMethod.Invoke(xVal, new object[] { yVal }));
break;//Comparing finished.
}
}
}
else
{
if ((xHasVal == false) && (yHasVal == false))
res = 0;
else if ((xHasVal == false) && (yHasVal == true))
res = -1;
else if ((xHasVal == true) && (yHasVal == false))
res = 1;
}
}
return IsAsc ? res : -res;//Change the result according to the sort type.
}
}
This is the code snippet about the custom object and how to use the custom comparer class to sort the data source of the DataGridView:
Custom object:
public class People
{
public string FirstName { set; get; }
public string LastName { set; get; }
}
How to sort the data source:
ArrayList arrList = this.dataGridView1.DataSource as ArrayList;
MyComparable<People> peopleCompare = new MyComparable<People>();
peopleCompare.SortProperties.Add("FirstName");
peopleCompare.SortProperties.Add("LastName");
arrList.Sort(peopleCompare);
this.dataGridView1.Refresh();
These are some links:
IComparer: http://msdn.microsoft.com/en-us/library/system.collections.icomparer.aspx.
Comparer<T>: http://msdn.microsoft.com/en-us/library/cfttsh47.aspx.
Let me know if this helps.
Aland Li
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