Home > Articles > Programming > Windows Programming

This chapter is from the book

Defining Custom Column and Cell Types

With the DataGridView, you are already leaps and bounds ahead of the DataGrid for presenting rich data because of the built-in column types that it supports out of the box. But there are always custom scenarios that you will want to support to display custom columns. Luckily, another thing the DataGridView makes significantly easier is plugging in custom column and cell types.

If you want to customize just the painting process of a cell, but you don’t need to add any properties or control things at the column level, you have an event-based option rather than creating new column and cell types. You can handle the CellPainting event and draw directly into the cell itself, and you can achieve pretty much whatever you want with the built-in cell types and some (possibly complex) drawing code. But if you want to be able to just plug your column or cell type in a reusable way with the same ease as using the built-in types, then you can derive your own column and cell types instead.

The model you should follow for plugging in custom column types matches what you have already seen for the built-in types: You need to create a column type and a corresponding cell type that the column will contain. You do this by simply inheriting from the base DataGridViewColumn and DataGridViewCell classes, either directly or indirectly, through one of the built-in types.

The best way to explain this in detail is with an example. Say I wanted to implement a custom column type that lets me display the status of the items represented by the grid’s rows. I want to be able to set a status using a custom-enumerated value, and cells in the column will display a graphic indicating that status based on the enumerated value set on the cell. To do this, I define a StatusColumn class and a StatusCell class (I disposed of the built-in type naming convention here of prefixing DataGridView on all the types because the type names get sooooooooooo long). I want these types to let me simply set the value of a cell, either programmatically or through data binding, to one of the values of a custom-enumerated type that I call StatusImage. StatusImage can take the values Green, Yellow, or Red, and I want the cell to display a custom graphic for each of those based on the value of the cell. Figure 6.7 shows the running sample application with this behavior.


Figure 6.7 Custom Column and Cell Type Example

Defining a Custom Cell Type

To achieve this, the first step is to define the custom cell type. If you are going to do your own drawing, you can override the protected virtual Paint method from the DataGridViewCell base class. However, if the cell content you want to present is just a variation on one of the built-in cell types, you should consider inheriting from one of them instead. That is what I did in this case. Because my custom cells are still going to be presenting images, the DataGridViewImageCell type makes a natural base class. My StatusCell class isn’t going to expose the ability to set the image at random, though; it is designed to work with enumerated values. I also want the cell value to be able to handle integers as long as they are within the corresponding numeric values of the enumeration, so that I can support the common situation where enumerated types are stored in a database as their corresponding integer values. The code in Listing 6.4 shows the StatusCell class implementation.

Example 6.4. Custom Cell Class

namespace CustomColumnAndCell
   public enum StatusImage

   public class StatusCell : DataGridViewImageCell
      public StatusCell()
         this.ImageLayout = DataGridViewImageCellLayout.Zoom;

      protected override object GetFormattedValue(object value,
         int rowIndex, ref DataGridViewCellStyle cellStyle,
         TypeConverter valueTypeConverter,
         TypeConverter formattedValueTypeConverter,
         DataGridViewDataErrorContexts context)

         string resource = "CustomColumnAndCell.Red.bmp";
         StatusImage status = StatusImage.Red;
         // Try to get the default value from the containing column
         StatusColumn owningCol = OwningColumn as StatusColumn;
         if (owningCol != null)
            status = owningCol.DefaultStatus;
         if (value is StatusImage || value is int)
            status = (StatusImage)value;
         switch (status)
            case StatusImage.Green:
               resource = "CustomColumnAndCell.Green.bmp";
               break;            case StatusImage.Yellow:
               resource = "CustomColumnAndCell.Yellow.bmp";
            case StatusImage.Red:
               resource = "CustomColumnAndCell.Red.bmp";
         Assembly loadedAssembly = Assembly.GetExecutingAssembly();
         Stream stream =
         Image img = Image.FromStream(stream);
         cellStyle.Alignment =
         return img;

The first declaration in this code is the enumeration StatusImage. That is the value type expected by this cell type as its Value property. You can then see that the StatusCell type derives from the DataGridViewImageCell, so I can reuse its ability to render images within the grid. There is a default status field and corresponding property that lets the default value surface directly. The constructor also sets the ImageLayout property of the base class to Zoom, so the images are resized to fit the cell with no distortion.

The key thing a custom cell type needs to do is either override the Paint method, as mentioned earlier, or override the GetFormattedValue method as the StatusCell class does. This method will be called whenever the cell is rendered and lets you handle transformations from other types to the expected type of the cell. The way I have chosen to code GetFormattedValue for this example is to first set the value to a default value that will be used if all else fails. The code then tries to obtain the real default value from the containing column’s DefaultValue property if that column type is StatusColumn (discussed next). The code then checks to see if the current Value property is a StatusImage enumerated type or an integer, and if it is an integer, it casts the value to the enumerated type.

Once the status value to be rendered is determined, the GetFormattedValue method uses a switch-case statement to select the appropriate resource name corresponding to the image for that status value. You embed bitmap resources in the assembly by adding them to the Visual Studio project and setting the Build Action property on the file to Embedded Resource. The code then uses the GetManifestResourceStream method on the Assembly class to extract the bitmap resource out of the assembly, sets the alignment on the cellStyle argument passed into the method, and then returns the constructed image as the object from the method. The object that you return from this method will be the one that is passed downstream to the Paint method as the formatted value to be rendered. Because this doesn’t override the Paint method, the implementation of my DataGridViewImageCell base class will be called, and it expects an Image value to render.

Defining a Custom Column Type

So now you have a custom cell class that could be used in the grid, but you also want to have a custom column class that contains StatusCells and can be used for setting up the grid and data binding. If you were going to use the custom cell type completely programmatically, you could just construct an instance of the DataGridViewColumn base class and pass in an instance of a StatusCell to the constructor, which sets that as the CellTemplate for the column. However, that approach wouldn’t let you use the designer column editors covered in Figures 6.4 and 6.5 to specify a bound or unbound column of StatusCells. To support that, you need to implement a custom column type that the designer can recognize. As long as you’re implementing your own column type, you also want to expose a way to set what the default value of the StatusImage should be for new rows that are added. The implementation of the StatusColumn class is shown in Listing 6.5.

Example 6.5. Custom Column Class

namespace CustomColumnAndCell
   public class StatusColumn : DataGridViewColumn
      public StatusColumn() : base(new StatusCell())
      private StatusImage m_DefaultStatus = StatusImage.Red;

      public StatusImage DefaultStatus
         get { return m_DefaultStatus; }
         set { m_DefaultStatus = value; }

      public override object Clone()
         StatusColumn col = base.Clone() as StatusColumn;
         col.DefaultStatus = m_DefaultStatus;
         return col;

      public override DataGridViewCell CellTemplate
         get { return base.CellTemplate; }
           if ((value == null) || !(value is StatusCell))
              throw new ArgumentException(
   "Invalid cell type, StatusColumns can only contain StatusCells");

You can see from the implementation of StatusColumn that you first need to derive from the DataGridViewColumn class. You implement a default constructor that passes an instance of your custom cell class to the base class constructor. This sets the CellTemplate property on the base class to that cell type, making it the cell type for any rows that are added to a grid containing your column type.

The next thing the class does is define a public property named DefaultStatus. This lets anyone using this column type to set which of the three StatusImage values should be displayed by default if no value is explicitly set on the grid through data binding or programmatic value setting on a cell. The setter for this property changes the member variable that keeps track of the current default. The DefaultStatus property on the column is accessed from the StatusCell.GetFormattedValue method, as described earlier.

Another important thing for you to do in your custom column type is to override the Clone method from the base class, and in your override, return a new copy of your column with all of its properties set to the same values as the current column instance. This method is used by the design column editors to add and edit columns in a grid through the dialogs discussed in Figures 6.4 and 6.5.

The last thing the custom column class does is to override the CellTemplate property. If someone tries to access the CellTemplate, the code gets it from the base class. But if someone tries to change the CellTemplate, the setter checks to see if the type of the cell being set is a StatusCell. If not, it raises an exception, preventing anyone from programmatically setting an inappropriate cell type for this column. This doesn’t prevent you from mixing other cell types into the column for a heterogeneous grid (as shown earlier in the section on programmatically creating the grid).

Now that you have defined the custom cell and column types, how can you use them? Well, you can define them as part of any Windows application project type in Visual Studio, but generally when you create something like this, you are doing it so you can reuse it in a variety of applications. Whenever you want reuse code, you need to put that code into a class library. So if you define a class library project, add the classes just discussed to the class library, along with the images you want to use for displaying status as embedded resources in the project. This creates an assembly that you can then reference from any Windows application that you want to use the column and cell type within. All you need to do is set a reference to that assembly from the Windows Forms project in which you want to use them, and the custom column types will display in the Add Column dialog, as shown in Figure 6.8 (StatusColumn, in this case).


Figure 6.8 Custom Column Types in the Add Column Dialog

Within your Windows Forms application, you can programmatically add StatusColumns to a grid, or use the designer to do so. If you add the column through the designer and then look at it in the Edit Columns dialog, you will see that DefaultStatus appears in the property list and is settable as an enumerated property with its allowable values (see Figure 6.9).


Figure 6.9 Custom Column Properties in the Edit Columns Dialog

With a column of this type added to the grid, you can either populate the grid programmatically with either of the types that the cell is able to handle for values (either StatusImage values or integers within the value range of StatusImage), or you can data bind to it with a collection of data that contains those values. Here is a simple example of setting the values programmatically on a grid containing two columns: a text box column and a StatusColumn. Note that you can set the values with either the enumerated value or with an appropriate integer value.

m_Grid.Rows.Add("Beer Bottler", StatusImage.Green);
m_Grid.Rows.Add("Beer Bottle Filler", 1); //StatusImage.Yellow = 1
m_Grid.Rows.Add("Bottle capper", StatusImage.Red);

The CustomColumnAndCell sample application in the download code also demonstrates creating a data set and data binding against the status column.

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information

To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.


Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.


If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information

Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.


This site is not directed to children under the age of 13.


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information

If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information

Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents

California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure

Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact

Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice

We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020