5. Windows Forms Datagrid

5.1 How can I programatically set the rowheight of a row in my DataGrid?

You can do this by starting a new thread and executing Application.Run for the status dialog form when the background thread starts running. To communicate changes in percentage use BeginInvoke to executes a specific delegate asynchronously on the thread that the form was created on.

Download the ProgressThread progressthread.zip sample for a complete implementation of a BackgroundThreadStatusDialog class that shows a status dialog in a separate thread.

In order to use BackgroundThreadStatusDialog from your code you have to update the Progress inside your loop and check the IsCanceled state to detect if the user pressed the Cancel button.

5.2 How can I autosize the rowheights in my datagrid?

Here is a solution suggested by Matthew Benedict. It uses reflection to access the protected DataGridRows collection so he can set the row height.

5.3 How do I prevent sorting a single column in my DataGrid?

You can implement the IMessageFilter interface in your main form. This amounts to adding an override for PreFilterMessage, and looking for the particular message you need to catch. Here are code snippets that catch an escape key on a keydown. You can download a sample project(C#, VB). In the sample, there are two forms, with several controls. You'll notice that no matter what form or control has input focus, the escape key is caught in the PreFilterMessage override.

5.4 How do I programmatically select a row in DataGrid?

We have a small sample that shows how to do this. Download PropTab.zip. After you download and unzip the sample, build the project. Both the control assembly and a small driver assembly get built. After that add the control to your toolbox using 'Customise toolbox...'. Then drag and drop an instance of the added control onto the form in the driver winforms sub-project. When you select this control the properties window should have a tab with a bitmap 'T' as shown below.

These are the steps involved. Before following these steps please download and take a look at the sample. That will greatly help when following these steps.

Control related steps

Assume that you have a control that has two sets of properties, one set that you wish to have displayed in the main property tab and another set that you wish to have displayed in the second tab.

• Mark those properties that you wish to display in the first tab with the BrowsableAttribute to true.
• Mark those properties that you wish to display in the second tab with the BrowsableAttribute set to false. Create another attribute. Name it anything you want and give it a single boolean property. Initialize this property to true.

Other steps

• Derive a class from System.Windows.Forms.PropertyGridInternal.PropertiesTab. You have to override a few methods. The most important of these is GetProperties. We override GetProperties as shown below to use our CustomAttribute as the filtering attribute instead of the BrowsableAttribute that the PropertyGrid uses by default.

5.5 How can I translate a point to a cell in the datagrid?

PE refers to portable executable. The file format used for executable programs and for files to be linked together to form executable programs. It includes both metadata information that describes types and members referenced in your program, and the MSIL that is the code base for the program. Source: .NET Framework SDK Documentation

5.6 I lost the settings in my DataGrid set during design-time?

This is possible if you assign a custom DataGridTableStyle to the DataGrid. The properties in the DataGridTableStyle will then replace certain properties in the DataGrid. Take a look at DataGrid class reference for a list of these properties.

5.7 How do I prevent a click into the grid highlighting a cell?

Here is a technique for binding an arraylist of objects where the objects contain public property that can appear as columns in the datagrid. In this example, the object contains 2 public doubles, one named value and the other named sqrt. To bind this arraylist to a datagrid, add a custom tablestyle that has a MappingName of "ArrayList", and then use the property names as the MappingName for each column. Below are some code snippets. You can download a working project that also has code to delete rows and add new rows to the bound arraylist.

5.8 How do I prevent the datagrid from displaying its append row (the row at the end with an asterisk)?

The DataGrid class does not have a property that controls whether a new row can be added. But the DataView class does have such a property (along with some others such as AllowEdit and AllowDelete). Here is code that will turn off the append row by getting at the dataview associated with the datagrid.

If your datagrid contains links, then Matthew Miller suggest adding Navigate handler such as the one below to disallow the AddNew.

5.9 How can I catch a double-click into a column header cell?

You can use the DataGrid's double-click event and its HitTest method to catch a double click on a header.

5.10 How can I select the entire row when the user clicks on a cell in the row?

Call the DataGrid.Select method from within its mouseup event.

5.11 How can I get text from a column header in a MouseUp event?

5.12 How do I hide a column?

There are several ways to hide a column:

1) You can use your DataSet's ColumnMapping property to hide a column.

2) Another way to hide a column is to set its width to zero. Check out the FAQ How do I set the width of a column in my DataGrid?.

3) Another way to hide a column is to create a custom table style, and as you add columnstyles to your tablestyle, omit the column you want hidden. Check out the FAQ How do I add an unbound column in my bound DataGrid? to see how to create a custom table style.

5.13 How do I color a individual cell depending upon its value or some external method?

We give three different methods for doing this.