AutoComplete Brackets In C#.NET/VB .NET

 

 

Step 1:  Start Visual Studio and create Windows Form Application in C# or VB as you wish.

 

Step 2: Add CheckBox and RichTextBox to your form.

 

Step 3:  Add  KeyPress and KeyDown events to RichTextBox.

 

Step 4: Now add the following code defined in KeyPress and KeyDown event into your code.

How it Works

It's simple, just identify which key is pressed in richTextBox, if it is ( open round bracket then read SelectionStart from richTextBox and insert opposite character to richTextBox at position SelectionStart+1.

Finally add one line once opposite character is inserted and that is e.Handled=true;  

C# Code for Auto Complete Brackets,

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Windows.Forms;

namespace Auto_Complete_Brackets
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        //declare  isCurslyBracesKeyPressed variable as Boolean and assign false value
        //to check { key is pressed or not
        public static Boolean isCurslyBracesKeyPressed = false;

        //richTextBox1 KeyPress events

        // if key (,{,<,",',[ is pressed then insert opposite key to richTextBox1 at Position SelectionStart+1
        // add one line after inserting, e.Handled=true;
        //finally set SelectionStart to specified position

        private void richTextBox1_KeyPress(object sender, KeyPressEventArgs e)
        {
            String s = e.KeyChar.ToString();
            int sel = richTextBox1.SelectionStart;
            if (checkBox1.Checked == true)
            {
                switch (s)
                {
                    case "(": richTextBox1.Text = richTextBox1.Text.Insert(sel, "()");
                        e.Handled = true;
                        richTextBox1.SelectionStart = sel + 1;
                        break;

                    case "{":
                        String t = "{}";
                        richTextBox1.Text = richTextBox1.Text.Insert(sel, t);
                        e.Handled = true;
                        richTextBox1.SelectionStart = sel + t.Length - 1;
                        isCurslyBracesKeyPressed = true;
                        break;

                    case "[": richTextBox1.Text = richTextBox1.Text.Insert(sel, "[]");
                        e.Handled = true;
                        richTextBox1.SelectionStart = sel + 1;
                        break;

                    case "<": richTextBox1.Text = richTextBox1.Text.Insert(sel, "<>");
                        e.Handled = true;
                        richTextBox1.SelectionStart = sel + 1;
                        break;

                    case "\"": richTextBox1.Text = richTextBox1.Text.Insert(sel, "\"\"");
                        e.Handled = true;
                        richTextBox1.SelectionStart = sel + 1;
                        break;

                    case "'": richTextBox1.Text = richTextBox1.Text.Insert(sel, "''");
                        e.Handled = true;
                        richTextBox1.SelectionStart = sel + 1;
                        break;
                }
            }
        }


        // richTextBox1 Key Down event
        /*
         * when key  {  is pressed and {} is inserted in richTextBox
         * and isCurslyBracesKeyPressed is true then insert some blank text to richTextBox1
         * when Enter key is down
         * it will look like this when Enter key is down

             {
                   |
             }

         * */

        private void richTextBox1_KeyDown(object sender, KeyEventArgs e)
        {
            int sel = richTextBox1.SelectionStart;
            if (e.KeyCode == Keys.Enter)
            {
                if(isCurslyBracesKeyPressed==true)
                {
                    richTextBox1.Text = richTextBox1.Text.Insert(sel, "\n          \n");
                    e.Handled = true;
                    richTextBox1.SelectionStart = sel + "          ".Length;
                    isCurslyBracesKeyPressed = false;
                }
            }
        }
    }
}

VB.Net Code for Auto Complete Brackets

Imports System
Imports System.Collections.Generic
Imports System.ComponentModel
Imports System.Data
Imports System.Drawing
Imports System.Windows.Forms
Public Class Form1

    'declare  isCurslyBracesKeyPressed variable as Boolean and assign false value
    'to check { key is pressed or not
    Public Shared isCurslyBracesKeyPressed As [Boolean] = False

    'RichTextBox1 KeyPress events

    ' if key (,{,<,",',[ is pressed then insert opposite key to RichTextBox1 at Position SelectionStart+1
    ' add one line after inserting, e.Handled=true;
    'finally set SelectionStart to specified position

    Private Sub RichTextBox1_KeyPress(sender As Object, e As KeyPressEventArgs) Handles RichTextBox1.KeyPress
        Dim s As [String] = e.KeyChar.ToString()
        Dim sel As Integer = RichTextBox1.SelectionStart
        If checkBox1.Checked = True Then
            Select Case s
                Case "("
                    RichTextBox1.Text = RichTextBox1.Text.Insert(sel, "()")
                    e.Handled = True
                    RichTextBox1.SelectionStart = sel + 1
                    Exit Select

                Case "{"
                    Dim t As [String] = "{}"
                    RichTextBox1.Text = RichTextBox1.Text.Insert(sel, t)
                    e.Handled = True
                    RichTextBox1.SelectionStart = sel + t.Length - 1
                    isCurslyBracesKeyPressed = True
                    Exit Select

                Case "["
                    RichTextBox1.Text = RichTextBox1.Text.Insert(sel, "[]")
                    e.Handled = True
                    RichTextBox1.SelectionStart = sel + 1
                    Exit Select

                Case "<"
                    RichTextBox1.Text = RichTextBox1.Text.Insert(sel, "<>")
                    e.Handled = True
                    RichTextBox1.SelectionStart = sel + 1
                    Exit Select

                Case """"
                    RichTextBox1.Text = RichTextBox1.Text.Insert(sel, """""")
                    e.Handled = True
                    RichTextBox1.SelectionStart = sel + 1
                    Exit Select

                Case "'"
                    RichTextBox1.Text = RichTextBox1.Text.Insert(sel, "''")
                    e.Handled = True
                    RichTextBox1.SelectionStart = sel + 1
                    Exit Select
            End Select
        End If
    End Sub


    ' RichTextBox1 Key Down event
    '
    '         * when key  {  is pressed and {} is inserted in richTextBox
    '         * and isCurslyBracesKeyPressed is true then insert some blank text to RichTextBox1
    '         * when Enter key is down
    '         * it will look like this when Enter key is down
    '
    '             {
    '                   |
    '             }
    '
    '         *

    Private Sub RichTextBox1_KeyDown(sender As Object, e As KeyEventArgs) Handles RichTextBox1.KeyDown
        Dim sel As Integer = RichTextBox1.SelectionStart
        If e.KeyCode = Keys.Enter Then
            If isCurslyBracesKeyPressed = True Then
                RichTextBox1.Text = RichTextBox1.Text.Insert(sel, vbLf & "          " & vbLf)
                e.Handled = True
                RichTextBox1.SelectionStart = sel + "          ".Length
                isCurslyBracesKeyPressed = False
            End If
        End If
    End Sub
End Class