Skip to main content

WinForms, how to implement conditional format for DataGridViews

Being able to apply conditional formats to datagridviews is a must nowadays, users of our app probably make heavy use of this feature on Excel spreadsheets, and they want it to be present on any "grid alike" screen.

I’ll show you two ways to implement this feature the first one is using pre-built formats, or formats specified in C# at compile time (better performance) and the second one that allows users to add their own conditional formats with formulas written in an excel fashion. In the last case the performance is not good enough for prod., but I’ll be sanding rough edges and hopefully make it work in a near future.

To work on this feature, I'm going to use the same datagrid I used in the previous post, which you can download from here.

The whole functionality is already implemented, so I'll just show you how to use it.

The only thing you have to do is register the conditional format and the component will take care of the rest. To register a conditional format you have to specify a function (the conditional part) and the format to be applied if the function result is true. Something like this:

In order to apply all of the specified formats, we need to hook an event handler to the grid’s RowPrePaint event and evaluate each registered condition, if the result is true, the format is applied. (The component takes care of this; you don't have to do anything. It's just an implementation detail)

And this is the layout of our little sample.

In the next post, how to implement this behavior for user defined conditional formats.


Popular posts from this blog

How to create MS Word documents from Office templates using C#

The OpenXML SDK allows you to do pretty much anything you want with office files such as Excel, Word, etc… While many people like this library, I found it complex, unintuitive and poorly documented, not to mention the awful xml format that uses under the hood to represent the documents, styles, etc. So I decided not to use it and build my own solution. If you, like me, don’t like that library, you will find in this post an alternative approach to build word documents from templates using c#.
A neat trick to work with Office is to use the macro recorder to understand how things work. The macro recorder allows you to start a macro, do something by hand, stop it, and then take a look at the generated VBA code. Once you do this, you are pretty much set.
This is how it looks the template I’am going to use.

Note: save the file as a Word template (.dotx)
This is the code to create Word documents from C#:

By running the code, you should get a document that looks like this.

Note that the font, forma…

Printing html using the embedded web browser control

In this post I’ll try to answer some questions about the web browser control and provide some workarounds for known issues involved in the printing process.
I'm assuming that you have some experience with the web browser control and basic knowledge of COM and hosting APIs. So I’m not going to cover those topics.
At the bottom of this page I’ve added the links to download a small library I wrote that takes care of printing HTML and a demo app so you can try it out without having to write any code by yourself.
Using the code The HtmlPrinter class will allow you to print html from an URL or just passing the html as string, you can also specify the title and the number of copies you want to print. The code may look something like this: Now that we know how to use the API let get answer some questions.
Why my app crashes when I try to print multiple copies of a page? Well, apparently when you send a lot of print commands to the web browser control, there is a lot of COM crap in between that l…

WinForms, paging the DataGridView the right way

I know this may sound like old history, but in the enterprise world there is still a lot of WinForms development. Just a couple of days ago, I had to implement a custom DataGridView capable to work over a butt load of data (100K+ records) and keep responses times acceptables.
I thought paging will be a good way to go, and as WinForms is pretty old nowadays, I supposed it will be easy to find a couple examples on the web.
While in fact I found examples, all of them were incompletes and/or they wouldn't perform well in real world apps... So I decided to roll my own component and post it online. Hopefully, someone else will find it useful ;).

The bread and butter of this solution relies on LINQ and deferred execution. As LINQ takes care of all complicated work, it was quite easy to implement.
This component also supports conditional format, sorting and some search capabilities, but in this post I will concentrate on paging only (I'll cover the rest of the features in future posts)…