Add hexadecimal color convert

Author: Suiram1701

API.Test/ExtensionsTests/ColorExtensionsTests.cs

@@ -0,0 +1,37 @@
+using System;
+using System.Collections.Generic;
+using System.Drawing;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using WebUntisAPI.Client.Extensions;
+
+namespace API.Test.ExtensionsTests;
+
+[TestFixture]
+internal class ColorExtensionsTests
+{
+    [Test]
+    public void ToHexColorFormat()
+    {
+        // Example 1
+        Color c1 = Color.FromArgb(200, 150, 255);
+        Assert.That(c1.ToHexColorFormat(), Is.EqualTo("C896FF"));
+
+        // Example 2
+        Color c2 = Color.FromArgb(10, 16, 0);
+        Assert.That(c2.ToHexColorFormat(), Is.EqualTo("0A1000"));
+    }
+
+    [Test]
+    public void FromHexColorFormat()
+    {
+        // Example 1
+        Color c1 = Color.FromArgb(200, 150, 255);
+        Assert.That(new Color().FromHexColorFormat("C896FF"), Is.EqualTo(c1));
+
+        // Example 2
+        Color c2 = Color.FromArgb(10, 16, 0);
+        Assert.That(new Color().FromHexColorFormat("0A1000"), Is.EqualTo(c2));
+    }
+}

WebUntisAPI.Client/Extensions/ColorExtensions.cs

@@ -0,0 +1,46 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using System.Drawing;
+using System.Text.RegularExpressions;
+
+namespace WebUntisAPI.Client.Extensions
+{
+    /// <summary>
+    /// Extensions for the <see cref="Color"/> struct
+    /// </summary>
+    public static class ColorExtensions
+    {
+        /// <summary>
+        /// Convert a color instance to the Hexadeciaml format: RRGGBB
+        /// </summary>
+        /// <param name="color"></param>
+        /// <returns>The color string</returns>
+        public static string ToHexColorFormat(this Color color)
+        {
+            return color.R.ToString("X2") + color.G.ToString("X2") + color.B.ToString("X2");
+        }
+
+        /// <summary>
+        /// Convert a color string to the Hexadecimal format: RRGGBB
+        /// </summary>
+        /// <param name="color"></param>
+        /// <returns>The created color</returns>
+        /// <exception cref="ArgumentException">Thrown when the <paramref name="colorString"/> isn't in the correct format</exception>
+        public static Color FromHexColorFormat(this Color color, string colorString)
+        {
+            if (!Regex.IsMatch(colorString, @"[\da-fA-F]{6}"))
+                throw new ArgumentException("The color string isn't in a correct format", nameof(colorString));
+
+            // Convert the hex string to the single color channels
+            int red = Convert.ToByte(colorString.Substring(0, 2), 16);
+            int green = Convert.ToByte(colorString.Substring(2, 2), 16);
+            int blue = Convert.ToByte(colorString.Substring(4, 2), 16);
+
+            return Color.FromArgb(red, green, blue);
+        }
+    }
+
+}