JRCookbook/JRCookbookControls/JRCookbookAutoVerticalGrowTextBox.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.ComponentModel;

namespace JRCookbookControls
{
    [System.Serializable()]
    public class JRCookbookAutoVerticalGrowTextBox : TextBox
    {
        private int _MinCharactersToMultiLine = 0;

        public JRCookbookAutoVerticalGrowTextBox()
        {
            this.Multiline = (this.Text.Length >= _MinCharactersToMultiLine);

            this.TextChanged += JRCookbookAutoVerticalGrowTextBox_TextChanged;
            this.MultilineChanged += JRCookbookAutoVerticalGrowTextBox_MultilineChanged;
            this.Resize += JRCookbookAutoVerticalGrowTextBox_Resize;

        }

        [DesignerSerializationVisibility(DesignerSerializationVisibility.Visible)]
        public int MinCharactersToMultiLine
        {
            get
            {
                return _MinCharactersToMultiLine;
            }
            set
            {
                _MinCharactersToMultiLine = value;
                this.Multiline = (this.Text.Length >= _MinCharactersToMultiLine);
            }
        }




        private void JRCookbookAutoVerticalGrowTextBox_Resize(object sender, EventArgs e)
        {
            RecalculateTextBoxHeight();
        }

        private void JRCookbookAutoVerticalGrowTextBox_TextChanged(System.Object sender, System.EventArgs e)
        {
            this.Multiline = (this.Text.Length >= _MinCharactersToMultiLine);
            RecalculateTextBoxHeight();
        }

        private void JRCookbookAutoVerticalGrowTextBox_MultilineChanged(System.Object sender, System.EventArgs e)
        {
            //while we can't hide the multiline property, we can at least enforce its value.
            this.Multiline = (this.Text.Length >= _MinCharactersToMultiLine);
        }

        private void RecalculateTextBoxHeight()
        {
            // amount of padding to add
            const int padding = 3;
            // get number of lines (first line is 0, so add 1)
            int numLines = this.GetLineFromCharIndex(this.TextLength) + 1;
            // get border thickness
            int border = this.Height - this.ClientSize.Height;
            // set height (height of one line * number of lines + spacing)
            this.Height = this.Font.Height * numLines + padding + border;
        }

    }
}