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Cell Blink for DataGridView

, 4 May 2008 Zlib
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An article on adding a cell blink feature for DataGridView
Screenshot - DataGridViewCellBlink.jpg


After reading many articles on The Code Project, I realized that it's my time to contribute. Few months ago, I came across a requirement for cells in a DataGridView control to blink when the cell value changed. The code presented here can be applied to any other grid.

The blinking of the grid cell is achieved in the following manner. When we update the value of a cell, we also change the background color of that cell to a blink color. To restore the cell background color to its original value, we run a background thread that iterates through a list of cells that are blinking and resets them to their original non blinking state.

The Code

The sample project has two functions. The first function DataInputThreadFunc() is used to generate random values to be filled / updated in the grid. The second function GridBlinkThreadFunc() is used to restore the cells to the non blink state.

Let's take a look at the first function DataInputThreadFunc():

private void DataInputThreadFunc()
    Random rand = new Random();
    while (true)
        if (dataGridView1.IsDisposed)

        CellData data = new CellData();
        data.Row = rand.Next(0, 7);
        data.Col = rand.Next(0, 3);
        data.Time = DateTime.Now;

        int value = rand.Next(0, 101);

            dataGridView1.Rows[data.Row].Cells[data.Col].Value = value;
              .BackColor = Color.Salmon;

        lock (_blinkData)


The function uses a while (true) loop as it's a background thread and will be shutdown automatically when the application is closed. if (dataGridView1.IsDisposed) check is done to make sure we do not call dataGridView1.Invoke() on a disposed object. This can happen when the user closes the application.

Next, we initialize an object of the class CellData to store the blink data:

class CellData
     public int Row;
     public int Col;
     public DateTime Time;

This class is used to store the row number, column number and the time when the value changed.

Next we use dataGridView1.Invoke() to make a call to the user interface thread and set the grid properties. We save the blink data in a generic list to be used later by the blink thread function. Since the list is altered by more than one thread, we synchronize access by locking the list on each access.

Now let's take a look at the blink thread function:

private void GridBlinkThreadFunc()
    while (true)
        // Make a copy to avoid invalid operation exception
        // while iterating through the map
        List<CellData> tempBlinkData;
        lock (_blinkData)
            tempBlinkData = new List<CellData>(_blinkData);

        foreach (CellData data in tempBlinkData)
            TimeSpan elapsed = DateTime.Now - data.Time;
            if (elapsed.TotalMilliseconds > 500) // 500 is the Blink delay
                if (dataGridView1.IsDisposed)

                      .Style.BackColor = dataGridView1.Columns[data.Col]

                lock (_blinkData)

        Thread.Sleep(250); // Blink frequency

At the very beginning, we make a copy of the _blinkData list. This helps us to modify the list while we iterate through the contents of the temporary copy. For each cell we find in the list, we check to make sure whether the blink time has elapsed or not. In this case, the blink time is 500 milliseconds. Any cell that has elapsed the blink time gets its background color reset to the default cell style background color and is removed from the list.

Again we make sure that we set the grid property only in the user interface thread. In addition, we lock the _blinkData list before altering it. Thread.Sleep(250) is the frequency with which we go through the list to turn off the cells. Ideally, it should be half the value of blink delay.

Points of Interest

You will notice that this code can be applied to any grid. This code can also be hidden in a class that extends a DataGridView control.

One thing I love about .NET 2.0 is dataGridView1.Invoke((MethodInvoker)delegate(). This statement lets you get away from writing a function and declaring a delegate.

A good point was made by "Kristof Verbiest" about the use of BeginInvoke() instead of Invoke(). The GridBlinkThreadFunc() uses BeginInvoke() to avoid unnecessary context switch.


  • 09/06/2007: First published
  • 09/11/2007: Changed the GridBlinkThreadFunc() to use BeginInvoke() instead of Invoke()
  • 05/02/2008: Edited the "Points of Interest" section


This article, along with any associated source code and files, is licensed under The zlib/libpng License


About the Author

Rammohan Raja
United States United States
Nothing to brag about, just another passionate software developer.

Work to make a living, don't live to work!

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Comments and Discussions

GeneralPerformance issue Pin
Hoa Le10-Nov-08 16:19
memberHoa Le10-Nov-08 16:19 
GeneralRe: Performance issue Pin
Raghavan Ram Raja14-Nov-08 4:21
memberRaghavan Ram Raja14-Nov-08 4:21 
GeneralRe: Performance issue Pin
Hoa Le20-Nov-08 18:27
memberHoa Le20-Nov-08 18:27 
GeneralVB.NET Version Here (Visual Studio 2005) Pin
gratro14-Oct-08 3:26
membergratro14-Oct-08 3:26 
GeneralRe: VB.NET Version Here (Visual Studio 2005) Pin
Raghavan Ram Raja14-Oct-08 4:07
memberRaghavan Ram Raja14-Oct-08 4:07 
GeneralBlink Pin
txALI29-Jan-08 5:16
membertxALI29-Jan-08 5:16 
GeneralSome comments Pin
Kristof Verbiest10-Sep-07 21:16
memberKristof Verbiest10-Sep-07 21:16 
GeneralRe: Some comments Pin
Ram Mohan Raja11-Sep-07 5:42
memberRam Mohan Raja11-Sep-07 5:42 
1) I do agree that in the GridBlinkThreadFunc() I should use BeginInvoke() instead of Invoke() to avoid unnecessary context switch. I will update the code in the article. I disagree with your suggestion of avoiding Invoke() completely. Lets take a look at my other thread function DataInputThreadFunc(). Here I would insist on using Invoke(). The reason begin BeginInvoke() would cause this worker thread to run out of control and queue up UI updates on the GUI thread. This can happen if the GUI thread is blocked by the OS, to complete some high priority operation. Our worker thread would run uncontrolled. I generally do not prefer a runaway thread.

The use of Invoke() makes sure the worker thread is blocked if the UI thread is busy. This is a desired effect and I would use Invoke() in this case. Also there are many occasions when the UI needs to be updated immediately before the worker thread can proceed further.

Agreed that Invoke() is a double edged sword. If used incorrectly it will cause pains. A complete avoidance is not the solution either!

2) I come from a Visual C++, MFC/Win32 background. Those days system timers were precious resources! And if all the timers were used up then your application was doomed! Back then the good folks at MSDN suggested using worker threads as an alternative. It has been so ingrained in me that even though the timer limitations are gone in .NET, I still do not like them!

One more thing to note is that when the timer tick event is called all the code inside that event handler is getting executed in the UI thread. Using the precious UI thread to perform any lengthy operation is definitely a no-no. If you are writing code for a financial application which updates 20 times a second you will realize how busy the UI thread can get. If you add any lengthy operation on the timer tick event you can easily bring down the financial application!

The reason I make a copy of the List<celldata> is because I am using the foreach() statement to iterate through the list. And I also modify the list while iterating. This will cause an InvalidOperationException if I do not make the copy.

Thanks for your comments!Smile | :)

GeneralRe: Some comments Pin
Kristof Verbiest11-Sep-07 22:11
memberKristof Verbiest11-Sep-07 22:11 
GeneralRe: Some comments Pin
Ram Mohan Raja12-Sep-07 5:46
memberRam Mohan Raja12-Sep-07 5:46 

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