AddContextForm.cs

using System;
using System.Collections.Generic;
using Eto.Drawing;
using Eto.Forms;

namespace devtime
{
    public class AddContextForm : Dialog<bool>
    {
        public string? ContextName { get; private set; }
        private readonly TextBox _textBox;

        public AddContextForm()
        {
            Title = "Add project";
            Icon = IconLoader.LoadIcon("add.png");
            Resizable = false;

            _textBox = new TextBox { MaxLength = 255, Width = 150 };

            var okButton = new Button { Text = "OK", Width = 70, Height = 23 };
            okButton.Click += (sender, e) => OkClick();

            var cancelButton = new Button { Text = "Cancel", Width = 70, Height = 23 };
            cancelButton.Click += (sender, e) => Close(false);

            DefaultButton = okButton;
            AbortButton = cancelButton;

            var buttonLayout = new StackLayout
            {
                Orientation = Orientation.Horizontal,
                Spacing = 5,
                Items = { okButton, cancelButton }
            };

            Content = new StackLayout
            {
                Padding = new Padding(10, 5),
                Spacing = 5,
                HorizontalContentAlignment = HorizontalAlignment.Stretch,
                Items =
                {
                    new Label { Text = "Project name:" },
                    _textBox,
                    new StackLayout { HorizontalContentAlignment = HorizontalAlignment.Right, Items = { buttonLayout } }
                }
            };
        }

        private void OkClick()
        {
            string text = _textBox.Text.Trim();

            if (string.IsNullOrWhiteSpace(text))
            {
                MessageBox.Show(this, "The project name cannot be empty.", "devtime error", MessageBoxButtons.OK, MessageBoxType.Error);
                return;
            }

            if (text.Length > 255 || !IsValidProjectName(text))
            {
                MessageBox.Show(this, "Invalid project name (must only contain a-z, A-Z, 0-9 and underscores, with the first character not being a digit, and max 255 characters).\nPlease try another name.", "devtime error", MessageBoxButtons.OK, MessageBoxType.Error);
                return;
            }

            List<string> contexts = DB.ListTables();
            if (contexts.Contains(text))
            {
                MessageBox.Show(this, $"A project named '{text}' already exists.\nPlease try another name.", "devtime error", MessageBoxButtons.OK, MessageBoxType.Error);
                return;
            }

            ContextName = text;
            Close(true);
        }

        private bool IsValidProjectName(string str)
        {
            if (string.IsNullOrEmpty(str)) return false;
            for (int i = 0; i < str.Length; ++i)
            {
                char c = str[i];
                if (i == 0 && char.IsDigit(c)) return false;
                if (!char.IsLetterOrDigit(c) && c != '_') return false;
            }
            return true;
        }
    }
}