Bad news is better than no communication
January 20, 2011
January 8, 2011
Aggregation by rolling week
In my current project, we had interesting problem, customer wants to see few data aggregation by rolling week and not year week. Rolling week mean say today is ‘Saturday’, data should aggregate by all week ending ‘Saturday’, but if it was ‘Tuesday’, data should aggregate by by all week ending ‘Tuesday’. When I heard this for first time, I thought this going to end up real big and complex procedure. But to my surprise it’s not:
select customerId, bSaleDate as SaleDate, SUM(Amount) as Amount
from
(
select distinct
SaleByCustomerAndDate.customerId,
SaleSevenDayRange.SaleDate as bSaleDate,
SaleByCustomerAndDate.SaleDate as aSaleDate,
SaleByCustomerAndDate.Amount as Amount
from
(
select
customerId,
SaleDate,
SUM(Amount) as Amount
from
Sale
group by
customerId,
SaleDate
)
as SaleByCustomerAndDate inner join
(
select
customerId,
SaleDate,
DATEADD(DAY,-6,SaleDate) as LastSevenDay
from Sale
) as SaleSevenDayRange on SaleByCustomerAndDate.SaleDate
between
SaleSevenDayRange.LastSevenDay
and
SaleSevenDayRange.SaleDate
and SaleByCustomerAndDate.customerId = SaleSevenDayRange.customerId
) as c
group by
customerId,
bSaleDate
order by customerId, SaleDate
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January 5, 2011
ASP.NET Postback on table row click
When you need to go back to the server for further processing on clicking of a html element, for example on html table row click, below code may help you provide such functioning in ASP.NET.
Well, actually to allow control to support bubbling of the events, and allow user of the control to specify CommandName and CommandArgument while being used in template controls, there is some extract effort, essentially will need to implement IButtonControl. Let’s see the code below that I have implemented to provide function of selecting row when clicked on it.
1: [ToolboxData("<{0}:ListViewRowClickCommand CommandName=\"Select\" runat=\"server\"></{0}:ListViewRowClickCommand>")]
2: public class ListViewRowClickCommand : HtmlTableRow, IButtonControl, IPostBackEventHandler
3: {
4: public bool DisableCommand { get; set; }
5: protected override void Render(HtmlTextWriter writer)
6: {
7: writer.WriteBeginTag("tr");
8: if (ID != null)
9: writer.WriteAttribute("id", ClientID);
10: if (!DesignMode)
11: {
12: if (!DisableCommand)
13: writer.WriteAttribute("onclick", "javascript:" +
14: Page.ClientScript.GetPostBackEventReference(this, CommandArgument));
15: }
16: Attributes.Render(writer);
17: writer.Write(HtmlTextWriter.TagRightChar);
18:
19: RenderChildren(writer);
20: writer.WriteEndTag("tr");
21: }
22:
23: public bool CausesValidation
24: {
25: get { return (bool)(ViewState["CausesValidation"] ?? true); }
26: set { ViewState["CausesValidation"] = value; }
27: }
28:
29: public string CommandArgument
30: {
31: get { return (string)ViewState["CommandArgument"]; }
32: set { ViewState["CommandArgument"] = value; }
33: }
34:
35: public string CommandName
36: {
37: get { return (string)ViewState["CommandName"]; }
38: set { ViewState["CommandName"] = value; }
39: }
40:
41: public string PostBackUrl
42: {
43: get { return (string)ViewState["PostBackUrl"]; }
44: set { ViewState["PostBackUrl"] = value; }
45: }
46:
47: public string ValidationGroup
48: {
49: get { return (string)ViewState["ValidationGroup"]; }
50: set { ViewState["ValidationGroup"] = value; }
51: }
52:
53: public event EventHandler Click;
54: public event CommandEventHandler Command;
55:
56: public void RaisePostBackEvent(string eventArgument)
57: {
58: if (CausesValidation)
59: {
60: if (Page.IsPostBack)
61: Page.Validate();
62: if (!Page.IsValid)
63: return;
64: }
65:
66: OnClick(EventArgs.Empty);
67: OnCommand(new CommandEventArgs(CommandName, CommandArgument));
68: }
69:
70: protected virtual void OnCommand(CommandEventArgs eventArgs)
71: {
72: if (Command != null)
73: Command(this, eventArgs);
74:
75: RaiseBubbleEvent(this, eventArgs);
76: }
77:
78: protected virtual void OnClick(EventArgs eventArgs)
79: {
80: if (Click != null)
81: Click(this, eventArgs);
82: }
83: }
Above control can be used as below:
1: ...
2:
3: <asp:ListView ID="listViewOfSomething" runat="server" OnSelectedIndexChanging="OnSelectedIndexChanging">
4: <LayoutTemplate>
5: <table id="htmlTableOfSomething" >
6: <tbody>
7: <asp:PlaceHolder ID="itemPlaceholder" runat="server" />
8: </tbody>
9: </table>
10: </LayoutTemplate>
11: <ItemTemplate>
12: <vdd:ListViewRowClickCommand ID="ListViewRowClickCommand" runat="server"
13: CommandName="Select" Class="SomeCssClassForRow" >
14: <td class="CssClassForColumn">
15:
16: ...
Feel free to put comments in case if things are not clear.
April 18, 2010
Question your guesses and assumptions
It’s fare to guess or assume, in fact it helps moving forward in at least one direction, and is inevitable many a times. But started believing that a guess or assumption is truth, can be really harmful. Eventually questioning guesses and assumptions is important, and that also helps being open for multiple perspectives.
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February 2, 2010
Ignorance is not bliss. EventWaitHandle.OpenExisting throws WaitHandleCannotBeOpenedException
My development computer got upgraded to Windows 7, Windows 7 is good experience.
For one of our client, I needed to setup mechanics such that admin users should be able to initiate a process in Windows Service using GDI based .NET application. We had also developed the windows service in .NET. As both of them are .NET applications, there are more than one ways to IPC between them. As in this case there was only need to give signal to the service, I choose to do it through Windows Event. .NET BCL provides wrapper around Win32 functions to do this through type named EventWaitHandle.
I completed the code like I used to do in my old days, and tried the first use of it. On call to OpenExisting, client application failed with exception “No handle of the given name exists”. My first thought was that this could be because of UAC, but in that case it should say something like access violation. I tried running application in Windows 2003 Server and it worked perfectly. I decided to check documentation.
After some time I landed to msdn page for namespaces of kernel objects, which indicates that:
For processes started under a client session, the system uses the session namespace by default. However, these processes can use the global namespace by prepending the “Global\” prefix to the object name
changed my client code to have name prefixed with “Global\”, and everything started behaving the way I wanted it to in Windows 7 as well.
November 12, 2009
Extending code readability by extension methods
If you haven’t noticed, note that extension methods can also be called on null objects. Meaning, there can be extension method which checks whether an object is null or not. So,
public void Operate(InputType inputObject) { if (null != inputObject) { . . . } } public void Operate(InputType inputObject) { if (null == inputObject) { . . . } }
Can be replaced by
public void Operate(InputType inputObject) { if (inputObject.IsNotNull()) { . . . } } public void Operate(InputType inputObject) { if (inputObject.IsNull()) { . . . } }
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May 15, 2009
Sending email message having embedded image (.NET)
Does your .net application send email messages? Does it send formatted email messages? I think applications should always send formatted email messages instead of text only. (Are asking why? Simple, formatted messages are much more capable, presentable, …).
Counter argument: Some user uses email client that are not capable to show HTML messages. Or someone is doing it for security purpose. Okay, I agree, then send both the views; text view as well as HTML view. Using .NET, one can send multi view email messages, depending on email client settings and/or capability, client is expected to pick the right view and shows that to the user.
Next question is, say we have decided to send email in html and text view, can we send images and style sheets embedded with email? Answers is yes. Here is how one can send multi-part email message using .net libraries that has embedded image.
Here goes the first step, create MailMessage object and setup that with appropriate values
1: var from = new MailAddress("admin@objectpattern.com", "Himanshu");
2: var to = new MailAddress("himanshu@objectpattern.net");
3: var message = new MailMessage(from, to) { Subject = "Hi from ObjectPattern"};
next step changes. As we want to have two views – text and html, we will have to create email body differently.
in these lines of code, there are certain important points
1: //creating text view
2: var textViewContent = "Test content for text view";
3: var textView = AlternateView.CreateAlternateViewFromString(textViewContent, Encoding.UTF8,
4: MediaTypeNames.Text.Plain);
5: //creating html view
6: var htmlViewContent = " Html content containing image logo Thanks, ObjectPattern";
7: var htmlView = AlternateView.CreateAlternateViewFromString(htmlViewContent, Encoding.UTF8,
8: MediaTypeNames.Text.Html);
that I would like to bring in to your notice.
- Notice that we are not assigning Body property of MailMessage type
- While creating view, we are specifying media type name as either plain text or html text, it can also be rich text.
- We have created an img tag that referring to source as ‘cid:logo.png’
okay now how we will embed image into email message? That’s easy as well:
1: var logo = new LinkedResource("images/logo.png", MediaTypeNames.Image.Jpeg) {ContentId = "logo.png"};
2: htmlView.LinkedResources.Add(logo);
here in first line, first parameter of constructor (“image/logo.png” text) specifies the path of the image file. One can also supply image content as stream if its not coming directly from the file. Now remember, in above section, we had specified the src attribute of img tag, that should match with content id. Else image will not be shown correctly in email client. Also notice that we are adding this image to html view.
We are almost done now. All we need to do now is to add views to message object and sending using SMTP client.
1: message.AlternateViews.Add(textView);
2: message.AlternateViews.Add(htmlView);
3:
January 13, 2009
Changing version of .net framework dependency for setup and deployment project in visual studio 2008
Its easy to do, but not obvious to locate, at least to me. It took a while for me to find, so I thought let’s log it, in case if I need it in future, or someone else might need it. I need to create setup that depends on .NET framework 2.0. instead of 3.5 which is default in VS.NET 2008.
After creating setup and deployment project, double click on dependency of .net framework in solution explorer:
Now, you should be able to see launch condition for .net framework in “Launch Conditions” tab. Until you double click for the first time, node do not appear in launch conditions. And that’s where I wasted some hours:
Select the node and see the property window, where you will find the answer of the question:
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January 10, 2009
Knowing memory usage from Compact Framework application
For any handheld device application, memory usage is an important element to observer. .NET Compact framework have very less code that gives information about physical or virtual memory. But using native libraries – by doing pInvoke, one can retrieve memory usage statistics.
There can be more than one level of report that can be captured. Today, lets start with summary. GlobalMemoryStatus function in coredll can help identifying how much total physical memory available in the device and how much of it is free. Same way, how much of virtual memory available to process and how much of it is free.
Lets see how can we use GlobalMemoryStatus. We will have to define a class which will be passed to function and will be filled by GlobalMemoryStatus function. Layout of it is defined as structure by MS team, but its alright to use class here. By having it as class, we will be able to write default constructor unlike structure in C#.
[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Auto)]
internal class MemoryStatus
{
public uint dwLength;
public uint dwMemoryLoad;
public uint ullTotalPhys;
public uint ullAvailPhys;
public uint ullTotalPageFile;
public uint ullAvailPageFile;
public uint ullTotalVirtual;
public uint ullAvailVirtual;
public uint ullAvailExtendedVirtual;
public MemoryStatus()
{
this.dwLength = (uint)Marshal.SizeOf(typeof(MemoryStatus));
}
}
Now, lets define extern method for GlobalMemoryStatus
[return: MarshalAs(UnmanagedType.Bool)] [DllImport("coredll.dll", CharSet = CharSet.Auto, SetLastError = true, EntryPoint = "GlobalMemoryStatus")] static extern bool GlobalMemoryStatusWinCE([In, Out] MemoryStatus lpBuffer);
And here is how we can call the method
MemoryStatus internalReport = new MemoryStatus(); if (GlobalMemoryStatusWinCE(internalReport))
November 21, 2008
Navigate and injecting C# code using visual studio macro
Visual studio macros are great, probably I will write this in all posts that I write for macros :). Sometime back, I need to change a fairly big CF.NET application such a way that it will log a line on each function entry and on function exit. We were tracing for cause of intermittently occurring GWES.EXE error, and we were tracing it from multiple directions. The error code of GWES was 0xC0000005, which means someone was trying to access something, which was never allocated or is being accessed after releasing it. Application was multi-threaded, and hence it was difficult to understand which thread will do what at what time.
Moving back to original point, we wanted to log entry and exit of each functions. There can be more then one way to do that, but we have selected to change each functions. And to change each functions I have selected to use developer named “VS.NET macro”.
From macro it is possible to navigate through solution and projects. So macro first needs to find out all class types from a project, and then for each class, iterate through its member and find out functions that has body. If function has body, inject the code that logs line on function entry and exit.
It was easy to find function entry, but there can be many way function ends, like exception is being thrown, or based of some condition it may execute “return”, or body of the function is ended and hence return. To accommodate such cases, we decide to use “using statement” of C#.
All right, enough of the background, have look at Macro code here