Add option to skip null values when writing to Excel

README.md

@@ -551,6 +551,69 @@ File content before and after merge:
 ![before_merge_cells](https://user-images.githubusercontent.com/38832863/219970175-913b3d04-d714-4279-a7a4-6cefb7aa6ce8.PNG)
 ![after_merge_cells](https://user-images.githubusercontent.com/38832863/219970176-e78c491a-2f90-45a7-a4a2-425c5708d38c.PNG)
 
+#### 13. Skip null values
+
+Default behaviour:
+
+```csharp
+DataTable dt = new DataTable();
+
+/* ... */
+
+DataRow dr = dt.NewRow();
+
+dr["Name1"] = "Somebody once";
+dr["Name2"] = null;
+dr["Name3"] = "told me.";
+
+dt.Rows.Add(dr);
+
+MiniExcel.SaveAs(@"C:\temp\Book1.xlsx", dt);
+```
+
+![image](https://user-images.githubusercontent.com/31481586/241419441-c4f27e8f-3f87-46db-a10f-08665864c874.png)
+
+```xml
+<x:row r="2">
+    <x:c r="A2" t ="str" s="2">
+        <x:v>Somebody once</x:v>
+    </x:c>
+    <x:c r="B2" t ="str" s="2">
+        <x:v></x:v>
+    </x:c>
+    <x:c r="C2" t ="str" s="2">
+        <x:v>told me.</x:v>
+    </x:c>
+</x:row>
+```
+
+Result using new option:
+
+```csharp
+OpenXmlConfiguration configuration = new OpenXmlConfiguration()
+{
+     WriteNullValues = false // Default value is true.
+};
+
+MiniExcel.SaveAs(@"C:\temp\Book1.xlsx", dt, configuration: configuration);
+```
+
+![image](https://user-images.githubusercontent.com/31481586/241419455-3c0aec8a-4e5f-4d83-b7ec-6572124c165d.png)
+
+
+```xml
+<x:row r="2">
+    <x:c r="A2" t ="str" s="2">
+        <x:v>Somebody once</x:v>
+    </x:c>
+    <x:c r="B2" s="2"></x:c>
+    <x:c r="C2" t ="str" s="2">
+        <x:v>told me.</x:v>
+    </x:c>
+</x:row>
+```
+
+Works for null and DBNull values.
 
 ### Fill Data To Excel Template <a name="getstart3"></a>
 

docs/README.md

@@ -22,6 +22,9 @@
 
 ---
 
+### 1.30.4
+- [New] Support skipping null values when writing to Excel (via @0MG-DEN)
+
 ### 1.30.3
 - [New] support if/else statements inside cell (via @eynarhaji)
 

src/MiniExcel/OpenXml/ExcelOpenXmlSheetWriter.cs

@@ -395,14 +395,19 @@ private void GenerateSheetByColumnInfo<T>(MiniExcelStreamWriter writer, IEnumera
 
         private void WriteCell(MiniExcelStreamWriter writer, int rowIndex, int cellIndex, object value, ExcelColumnInfo p)
         {
-            var v = string.Empty;
-            var t = "str";
+            var columname = ExcelOpenXmlUtils.ConvertXyToCell(cellIndex, rowIndex);
             var s = "2";
-            if (value == null)
+
+            if (!_configuration.WriteNullValues && (value is null || value is DBNull))
             {
-                v = "";
+                writer.Write($"<x:c r=\"{columname}\" s=\"{s}\"></x:c>");
+                return;
             }
-            else if (value is string str)
+
+            var v = string.Empty;
+            var t = "str";
+
+            if (value is string str)
             {
                 v = ExcelOpenXmlUtils.EncodeXML(str);
             }
@@ -531,7 +536,6 @@ private void WriteCell(MiniExcelStreamWriter writer, int rowIndex, int cellIndex
                 }
             }
 
-            var columname = ExcelOpenXmlUtils.ConvertXyToCell(cellIndex, rowIndex);
             if (v != null && (v.StartsWith(" ", StringComparison.Ordinal) || v.EndsWith(" ", StringComparison.Ordinal))) /*Prefix and suffix blank space will lost after SaveAs #294*/
                 writer.Write($"<x:c r=\"{columname}\" {(t == null ? "" : $"t =\"{t}\"")} s=\"{s}\" xml:space=\"preserve\"><x:v>{v}</x:v></x:c>");
             else

src/MiniExcel/OpenXml/OpenXmlConfiguration.cs

@@ -16,6 +16,7 @@ public class OpenXmlConfiguration : Configuration
         public bool AutoFilter { get; set; } = true;
         public bool EnableConvertByteArray { get; set; } = true;
         public bool IgnoreTemplateParameterMissing { get; set; } = true;
+        public bool WriteNullValues { get; set; } = true;
         public bool EnableSharedStringCache { get; set; } = true;
         public long SharedStringCacheSize { get; set; } = 5 * 1024 * 1024;
     }