Clearer

ExcelORM/ExcelORM/ExcelDynamicReader.cs

@@ -14,7 +14,7 @@ public sealed class ExcelDynamicReader : IDisposable
         xlWorkbook = new XLWorkbook(path);
     }
 
-    public ExcelDynamicReader(IXLWorkbook workbook)
+    public ExcelDynamicReader(IXLWorkbook? workbook)
     {
         xlWorkbook = workbook ?? throw new ArgumentNullException(nameof(workbook));
     }

ExcelORM/ExcelORM/ExcelDynamicWriter.cs

@@ -12,7 +12,7 @@ public class ExcelDynamicWriter : IDisposable
         xlWorkbook = File.Exists(path) ? new XLWorkbook(path) : new XLWorkbook();
     }
 
-    public ExcelDynamicWriter(IXLWorkbook workbook)
+    public ExcelDynamicWriter(IXLWorkbook? workbook)
     {
         xlWorkbook = workbook ?? throw new ArgumentNullException(nameof(workbook));
     }

ExcelORM/ExcelORM/ExcelReader.cs

@@ -10,7 +10,7 @@ public class ExcelReader : IDisposable
     public bool SkipHidden { get; set; }
     public bool ObeyFilter { get; set; }
 
-    public ExcelReader(IXLWorkbook workbook)
+    public ExcelReader(IXLWorkbook? workbook)
     {
         xlWorkbook = workbook ?? throw new ArgumentNullException(nameof(workbook));
     }

ExcelORM/ExcelORM/ExcelWriter.cs

@@ -14,7 +14,7 @@ public class ExcelWriter : IDisposable
         xlWorkbook = File.Exists(path) ? new XLWorkbook(path) : new XLWorkbook();
     }
 
-    public ExcelWriter(IXLWorkbook workbook)
+    public ExcelWriter(IXLWorkbook? workbook)
     {
         xlWorkbook = workbook ?? throw new ArgumentNullException(nameof(workbook));
     }