Trying to simplify my List Collection Sort

[tshad]

I have dataGrid that I am filling from a List Collection and need to sort it
by the various columns.

So I need to be able to sort the Collection and found that you have to set
up your own sorting functions to make it work. I have build the following 3
sorting
functions for the 3 columns and have to call each one specifically.

I am trying to find a way to cut simplify the functions and calls to make
this a more
general class. At the moment, if I add another column I need to add another
sorting method
and another call from my switch.

Here is the Class and Sorts
*************** *************** *************** *
using System;
using System.Collecti ons.Generic;

namespace Irez
{
[Serializable()]
public class DisplayAmount : IComparable<Dis playAmount>
{
public DisplayAmount()
{
}
string mstrDisplayName = "";
double mdblDisplayValu e = 0;
string mstrTransaction Description = "";

public string DisplayName
{
get{ return mstrDisplayName ; }
set{ mstrDisplayName = value;}
}

public double DisplayValue
{
get{ return mdblDisplayValu e;}
set{ mdblDisplayValu e = value;}
}

public string TransactionDesc ription
{
get{ return mstrTransaction Description;}
set{ mstrTransaction Description = value;}
}

// Sorts
public static int CompareName(Dis playAmount c1, DisplayAmount c2)
{
return c1.DisplayName. CompareTo(c2.Di splayName);
}

public static int CompareValue(Di splayAmount c1, DisplayAmount c2)
{
return c1.DisplayValue .CompareTo(c2.D isplayValue);
}

public static int CompareTransact ionDescription( DisplayAmount c1,
DisplayAmount c2)
{
return
c1.TransactionD escription.Comp areTo(c2.Transa ctionDescriptio n);
}
}

// Define Collections here
public class DisplayAmountCo llection : List<DisplayAmo unt{ }
}
*************** *************** *************** ***************

To sort the collection I call the following function with the Collection,
the name of the column to sort and
the direction.

*************** *************** *************** *************** *
protected void SortList(ref DisplayAmountCo llection ocol, string
sortExpression, string sortDirection)
{
Comparison<Disp layAmountoColDe l = null;

switch (sortExpression )
{
case "DisplayNam e":
oColDel = new
Comparison<Disp layAmount>(Disp layAmount.Compa reName);
ocol.Sort(oColD el);
break;
case "DisplayVal ue":
oColDel = new
Comparison<Disp layAmount>(Disp layAmount.Compa reValue);
ocol.Sort(oColD el);
break;
case "TransactionDes cription":
oColDel = new
Comparison<Disp layAmount>(Disp layAmount.Compa reTransactionDe scription);
ocol.Sort(oColD el);
break;
}
if (sortDirection == "DESC") ocol.Reverse();
}
*************** *************** *************** *************** *

I'd like to see if I can simplify this if possible. If I have 10 columns, I
would have 10 case statements.

Also, I was trying to do a similar thing with my "Comparison<Dis playAmount>"
as I do with my "DisplayListCol lection".

I don't have to do:

List<DisplayAmo untd1 = null;

in my code. I put this in my class:

public class DisplayAmountCo llection : List<DisplayAmo unt{ }

and then call it in my program as:

DisplayAmountCo llection dc = null;

But I can't seem to the same with my Comparison<tsta tement without getting
an error. If I do the following:

public class DisplayAmountSo rt : Comparison<Disp layAmount{ }

I get the error:

cannot derive from sealed type 'System.Compari son<DisplayAmou nt>'

Why can I do it with List but not with Comparison?

Thanks,

Tom

[Ignacio Machin \( .NET/ C# MVP \)]

Hi,
If you are always going to sort by using only one column you can use a code
I created a time ago just for this:
http://groups.google.com/group/micro...97990b9dcd65e2

The good part about it is that the "sorted" class do not have knowledge of
it. you can sort a collection of ANY type.

You might ahve to convert it to use IComparer<Tas the code was created in
1.1

--
Ignacio Machin
http://www.laceupsolutions.com
Mobile & warehouse Solutions.
"tshad" <tf*@dslextreme .comwrote in message
news:uY******** ******@TK2MSFTN GP04.phx.gbl...

>I have dataGrid that I am filling from a List Collection and need to sort
it
by the various columns.

So I need to be able to sort the Collection and found that you have to set
up your own sorting functions to make it work. I have build the following
3 sorting
functions for the 3 columns and have to call each one specifically.

I am trying to find a way to cut simplify the functions and calls to make
this a more
general class. At the moment, if I add another column I need to add
another sorting method
and another call from my switch.

Here is the Class and Sorts
*************** *************** *************** *
using System;
using System.Collecti ons.Generic;

namespace Irez
{
[Serializable()]
public class DisplayAmount : IComparable<Dis playAmount>
{
public DisplayAmount()
{
}
string mstrDisplayName = "";
double mdblDisplayValu e = 0;
string mstrTransaction Description = "";

public string DisplayName
{
get{ return mstrDisplayName ; }
set{ mstrDisplayName = value;}
}

public double DisplayValue
{
get{ return mdblDisplayValu e;}
set{ mdblDisplayValu e = value;}
}

public string TransactionDesc ription
{
get{ return mstrTransaction Description;}
set{ mstrTransaction Description = value;}
}

// Sorts
public static int CompareName(Dis playAmount c1, DisplayAmount c2)
{
return c1.DisplayName. CompareTo(c2.Di splayName);
}

public static int CompareValue(Di splayAmount c1, DisplayAmount c2)
{
return c1.DisplayValue .CompareTo(c2.D isplayValue);
}

public static int CompareTransact ionDescription( DisplayAmount c1,
DisplayAmount c2)
{
return
c1.TransactionD escription.Comp areTo(c2.Transa ctionDescriptio n);
}
}

// Define Collections here
public class DisplayAmountCo llection : List<DisplayAmo unt{ }
}
*************** *************** *************** ***************

To sort the collection I call the following function with the Collection,
the name of the column to sort and
the direction.

*************** *************** *************** *************** *
protected void SortList(ref DisplayAmountCo llection ocol, string
sortExpression, string sortDirection)
{
Comparison<Disp layAmountoColDe l = null;

switch (sortExpression )
{
case "DisplayNam e":
oColDel = new
Comparison<Disp layAmount>(Disp layAmount.Compa reName);
ocol.Sort(oColD el);
break;
case "DisplayVal ue":
oColDel = new
Comparison<Disp layAmount>(Disp layAmount.Compa reValue);
ocol.Sort(oColD el);
break;
case "TransactionDes cription":
oColDel = new
Comparison<Disp layAmount>(Disp layAmount.Compa reTransactionDe scription);
ocol.Sort(oColD el);
break;
}
if (sortDirection == "DESC") ocol.Reverse();
}
*************** *************** *************** *************** *

I'd like to see if I can simplify this if possible. If I have 10 columns,
I would have 10 case statements.

Also, I was trying to do a similar thing with my
"Comparison<Dis playAmount>" as I do with my "DisplayListCol lection".

I don't have to do:

List<DisplayAmo untd1 = null;

in my code. I put this in my class:

public class DisplayAmountCo llection : List<DisplayAmo unt{ }

and then call it in my program as:

DisplayAmountCo llection dc = null;

But I can't seem to the same with my Comparison<tsta tement without
getting an error. If I do the following:

public class DisplayAmountSo rt : Comparison<Disp layAmount{ }

I get the error:

cannot derive from sealed type 'System.Compari son<DisplayAmou nt>'

Why can I do it with List but not with Comparison?

Thanks,

Tom

[Marc Gravell]

But if I am passing it with "ref", doesn't that say to pass it by reference

and not value?

This gets tricky to explain... the short version is that List<T(etc)
is a reference-type, which means that even without "ref" all you are
passing is the address of the list (on the managed heap). If you use
"ref" here, then instead of passing the address of the list, it passes
the address of the *variable* in the calling code (typically on the
stack, although it could be a field etc). The only things "ref" gives
you here is the ability to update the variable directly and have that
reassignment propegate to the calling method - but you don't need to
do that. Neither way (alone) causes the list to clone itself.

Jon Skeet puts it better: http://www.pobox.com/~skeet/csharp/parameters.html

Marc

[Marc Gravell]

Which cited links?

http://groups.google.com/group/micro...23312d4c9ae353
(this is for a BindingList<Tim plementation of IBindingList-based and
IBindingListVie w-based sorting, which is *exactly* what is used
automatically when you click on the column headers).

Marc