How to Autocomplete RichTextBox in C#

How to Autocomplete RichTextBox in C#

Open your Visual Studio, then create a new Windows Forms application project.

Next, Drag and drop a RichTextBox control from the Visual Studio toolbox to your windows forms application.

Next, You make your richtextbox autocomplete, then you can use the AutocompleteMenu library.

If you haven't already installed the Autocomplete Menu library, you can do so via NuGet Package Manager. Search for "AutocompleteMenu" and install the AutoCompleteMenu-ScintillaNET into your project.

Rebuild your project, then you can see the AutocompleteMenu control in your Visual Studio toolbox.

Finding the AutocompleteMenu control and add it to your form as well, then click on the RichTextBox control and set the AutocompleteMenu property to the autocompletemenu control. 

Adding items to the AutocompleteMenu control as shown above.

In your form's code, you need to initialize the AutocompleteMenu control and set up its properties, such as the data source and the column that will be used for autocomplete suggestions.