How Can I Implement a Full-String Search Autocomplete in C# Beyond Prefix-Only Matching?

Overcoming Prefix-Only Search Limitations in C# Autocomplete with Custom Logic

Despite the limitations of the built-in C# autocomplete functionality, it's possible to implement a custom autocomplete solution that allows you to search for results based on any part of the string. This is especially useful when incomplete or partial information is provided as input.

Custom Autocomplete Techniques

The standard autocomplete feature in C# operates only in prefix search mode, meaning it can only find matches that start with the entered text. To overcome this, you can implement your own autocomplete logic by overriding events such as OnTextChanged.

Example Implementation

An effective way to implement custom autocomplete is to use a ListBox to display potential matches. Here's a revised code snippet:

// Initialize list box
listBox1.Visible = false;
listBox1.SelectedIndexChanged += listBox1_SelectedIndexChanged;
listBox1.LostFocus += listBox1_LostFocus;

// Handle text changes in the text box
void textBox1_TextChanged(object sender, System.EventArgs e)
{
    listBox1.Items.Clear();
    if (textBox1.Text.Length == 0) {
        hideResults();
        return;
    }

    foreach (String s in textBox1.AutoCompleteCustomSource)
    {
        if (s.Contains(textBox1.Text))
        {
            listBox1.Items.Add(s);
            listBox1.Visible = true;
        }
    }
}

// Hide the list box on selection
void listBox1_SelectedIndexChanged(object sender, System.EventArgs e)
{
    textBox1.Text = listBox1.Items[listBox1.SelectedIndex].ToString();
    hideResults();
}

// Hide the list box when it loses focus
void listBox1_LostFocus(object sender, System.EventArgs e)
{
    hideResults();
}

// Hide the list box
void hideResults()
{
    listBox1.Visible = false;
}

Enhancements

The custom autocomplete solution provided in the example can be further enhanced by adding more functionality, such as:

• Appending matching text to the text box
• Capturing additional keyboard commands

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