Enhance API Documentation and Add Exception Handling

- Updated XML comments across various classes (Worksheet, Range, etc.) for improved API documentation.
- Added detailed descriptions, parameter info, and return types to the comments for better clarity in generated docs.
- Incorporated exception handling in methods where necessary, including validation checks for input arguments.
- Ensured consistency in commenting style to align with best practices in C# XML documentation.

Author: Fahad Adeel

FileFormat.Cells/Range.cs

@@ -15,19 +15,64 @@ public class Range
         public uint EndRowIndex { get; }
         public uint EndColumnIndex { get; }
 
-        // Returns the count of columns in the range
+        /// <summary>
+        /// Gets the count of columns in the range.
+        /// This property calculates the column count based on the start and end column indices.
+        /// </summary>
+        /// <value>
+        /// The count of columns in the range.
+        /// </value>
+        /// <exception cref="InvalidOperationException">
+        /// Thrown if the end column index is less than the start column index.
+        /// </exception>
         public uint ColumnCount
         {
-            get { return EndColumnIndex - StartColumnIndex + 1; }
+            get 
+            {
+                if (EndColumnIndex < StartColumnIndex)
+                {
+                    throw new InvalidOperationException("End column index cannot be less than start column index.");
+                }
+                return EndColumnIndex - StartColumnIndex + 1; 
+            }
         }
 
-        // Returns the count of rows in the range
+        /// <summary>
+        /// Gets the count of rows in the range.
+        /// This property calculates the row count based on the start and end row indices.
+        /// </summary>
+        /// <value>
+        /// The count of rows in the range.
+        /// </value>
+        /// <exception cref="InvalidOperationException">
+        /// Thrown if the end row index is less than the start row index.
+        /// </exception>
         public uint RowCount
         {
-            get { return EndRowIndex - StartRowIndex + 1; }
+            get
+            {
+                if (EndRowIndex < StartRowIndex)
+                {
+                    throw new InvalidOperationException("End row index cannot be less than start row index.");
+                }
+                return EndRowIndex - StartRowIndex + 1;
+            }
         }
 
-        
+        /// <summary>
+        /// Initializes a new instance of the Range class.
+        /// </summary>
+        /// <param name="worksheet">The worksheet to which this range belongs.</param>
+        /// <param name="startRowIndex">The starting row index of the range.</param>
+        /// <param name="startColumnIndex">The starting column index of the range.</param>
+        /// <param name="endRowIndex">The ending row index of the range.</param>
+        /// <param name="endColumnIndex">The ending column index of the range.</param>
+        /// <exception cref="ArgumentNullException">
+        /// Thrown if the provided worksheet is null.
+        /// </exception>
+        /// <exception cref="ArgumentOutOfRangeException">
+        /// Thrown if the start or end row/column indices are out of range.
+        /// </exception>
         public Range(Worksheet worksheet, uint startRowIndex, uint startColumnIndex, uint endRowIndex, uint endColumnIndex)
         {
             _worksheet = worksheet ?? throw new ArgumentNullException(nameof(worksheet));
@@ -37,6 +82,13 @@ public Range(Worksheet worksheet, uint startRowIndex, uint startColumnIndex, uin
             EndColumnIndex = endColumnIndex;
         }
 
+        /// <summary>
+        /// Sets the specified value to all cells within the range.
+        /// </summary>
+        /// <param name="value">The value to set in each cell of the range.</param>
+        /// <exception cref="InvalidOperationException">
+        /// Thrown if any cell within the range is not properly initialized or accessible.
+        /// </exception>
         public void SetValue(string value)
         {
             for (uint row = StartRowIndex; row <= EndRowIndex; row++)
@@ -50,6 +102,12 @@ public void SetValue(string value)
             }
         }
 
+        /// <summary>
+        /// Clears the values and resets the style of all cells within the range.
+        /// </summary>
+        /// <exception cref="InvalidOperationException">
+        /// Thrown if any cell within the range is not properly initialized or accessible.
+        /// </exception>
         public void ClearCells()
         {
             for (uint row = StartRowIndex; row <= EndRowIndex; row++)
@@ -67,6 +125,12 @@ public void ClearCells()
             }
         }
 
+        /// <summary>
+        /// Merges all cells within the range into a single cell.
+        /// </summary>
+        /// <exception cref="InvalidOperationException">
+        /// Thrown if the merge operation fails, for example, if the cells cannot be merged.
+        /// </exception>
         public void MergeCells()
         {
             string startCellReference = $"{ColumnIndexToLetter(StartColumnIndex)}{StartRowIndex}";
@@ -75,7 +139,16 @@ public void MergeCells()
             _worksheet.MergeCells(startCellReference, endCellReference);
         }
 
-
+        /// <summary>
+        /// Adds dropdown list validation with the specified options to all cells within the range.
+        /// </summary>
+        /// <param name="options">The list of options for the dropdown validation.</param>
+        /// <exception cref="ArgumentNullException">
+        /// Thrown if the options array is null or empty.
+        /// </exception>
+        /// <exception cref="InvalidOperationException">
+        /// Thrown if adding dropdown validation fails for any cell within the range.
+        /// </exception>
         public void AddDropdownListValidation(string[] options)
         {