Add ToBitArray overload with length

S7.Net/Types/Bit.cs

@@ -1,4 +1,5 @@
-using System.Collections;
+using System;
+using System.Collections;
 
 namespace S7.Net.Types
 {
@@ -16,12 +17,27 @@ namespace S7.Net.Types
         }
 
         /// <summary>
-        /// Converts an array of bytes to a BitArray
+        /// Converts an array of bytes to a BitArray.
         /// </summary>
-        public static BitArray ToBitArray(byte[] bytes)
+        /// <param name="bytes">The bytes to convert.</param>
+        /// <returns>A BitArray with the same number of bits and equal values as <paramref name="bytes"/>.</returns>
+        public static BitArray ToBitArray(byte[] bytes) => ToBitArray(bytes, bytes.Length * 8);
+
+        /// <summary>
+        /// Converts an array of bytes to a BitArray.
+        /// </summary>
+        /// <param name="bytes">The bytes to convert.</param>
+        /// <param name="length">The number of bits to return.</param>
+        /// <returns>A BitArray with <paramref name="length"/> bits.</returns>
+        public static BitArray ToBitArray(byte[] bytes, int length)
         {
-            BitArray bitArr = new BitArray(bytes);
-            return bitArr;
+            if (length > bytes.Length * 8) throw new ArgumentException($"Not enough data in bytes to return {length} bits.", nameof(bytes));
+
+            var bitArr = new BitArray(bytes);
+            var bools = new bool[length];
+            for (var i = 0; i < length; i++) bools[i] = bitArr[i];
+
+            return new BitArray(bools);
         }
     }
 }