Added WriteWithStartFrom

ExcelORM/ExcelORM/ExcelORM.csproj

@@ -4,7 +4,7 @@
         <TargetFramework>net8.0</TargetFramework>
         <ImplicitUsings>enable</ImplicitUsings>
         <Nullable>enable</Nullable>
-        <Version>2.8.0</Version>
+        <Version>2.8.1</Version>
         <PackageProjectUrl>https://git.liox.eu/pczajkowski/ExcelORM</PackageProjectUrl>
         <RepositoryUrl>https://github.com/pczajkowski/ExcelORM</RepositoryUrl>
         <GeneratePackageOnBuild>true</GeneratePackageOnBuild>
@@ -14,7 +14,7 @@
 	<Authors>Piotr Czajkowski</Authors>
 	<Description>Simple library to read/write C# objects from/to Excel files. </Description>
 	<RepositoryType>GitHub</RepositoryType>
-	<PackageReleaseNotes>Handling more number types. Properly handling appending to and reading from empty file.</PackageReleaseNotes>
+	<PackageReleaseNotes>Ability to start writing from given row.</PackageReleaseNotes>
     </PropertyGroup>
 
     <ItemGroup>

ExcelORM/ExcelORM/ExcelWriter.cs

@@ -19,9 +19,9 @@ public class ExcelWriter : IDisposable
         xlWorkbook = workbook ?? throw new ArgumentNullException(nameof(workbook));
     }
 
-    private static int GenerateHeader(IXLWorksheet worksheet, PropertyInfo[] properties)
+    private static int GenerateHeader(IXLWorksheet worksheet, PropertyInfo[] properties, uint? startFrom = null)
     {
-        var rowIndex = 1;
+        var rowIndex = startFrom == null ? 1 : (int)startFrom.Value;
         var cellIndex = 1;
         foreach (var property in properties)
         {
@@ -77,7 +77,7 @@ public class ExcelWriter : IDisposable
         }
     }
 
-    private static void Write<T>(IEnumerable<T> values, IXLWorksheet worksheet, bool append, uint? headerRowIndex = null, uint? appendFrom = null) where T : class
+    private static void Write<T>(IEnumerable<T> values, IXLWorksheet worksheet, bool append, uint? headerRowIndex = null, uint? startFrom = null) where T : class
     {
         var properties = typeof(T).GetProperties();
         List<Mapping>? mapping = [];
@@ -85,11 +85,11 @@ public class ExcelWriter : IDisposable
         var lastRow = worksheet.LastRowUsed();
         if (lastRow == null) append = false;
         
-        var rowIndex = (append, startFrom: appendFrom) switch
+        var rowIndex = (append, startFrom) switch
         { 
-            (true, not null) => (int)appendFrom,
+            (true, not null) => (int)startFrom,
             (true, null) => lastRow.RowNumber() + 1,
-            _ => GenerateHeader(worksheet, properties) 
+            _ => GenerateHeader(worksheet, properties, startFrom) 
         };
 
         if (append)
@@ -108,7 +108,7 @@ public class ExcelWriter : IDisposable
         }
     }
 
-    public void Write<T>(IEnumerable<T> values, string? worksheetName = null, bool append = false, uint? headerRowIndex = null, uint? appendFrom = null) where T : class
+    public void Write<T>(IEnumerable<T> values, string? worksheetName = null, bool append = false, uint? headerRowIndex = null, uint? startFrom = null) where T : class
     {
         var xlWorksheet = xlWorkbook.Worksheets.FirstOrDefault(x => x.Name.Equals(worksheetName, StringComparison.InvariantCultureIgnoreCase));
         
@@ -116,7 +116,7 @@ public class ExcelWriter : IDisposable
             xlWorkbook.AddWorksheet(worksheetName)
             : xlWorkbook.Worksheets.Count == 0 ? xlWorkbook.AddWorksheet() : xlWorkbook.Worksheets.First();
 
-        Write(values, xlWorksheet, append, headerRowIndex, appendFrom);
+        Write(values, xlWorksheet, append, headerRowIndex, startFrom);
     }
 
     public void SaveAs(string path, IExcelConverter? converter = null)

ExcelORM/ExcelORMTests/WriterTests.cs

@@ -101,7 +101,7 @@ public class WriterTests
 
         uint headerRowIndex = 3;
         using var writer = new ExcelWriter(testFile);
-        writer.Write(ArrayOfThree, append: true, headerRowIndex: headerRowIndex, appendFrom: 7);
+        writer.Write(ArrayOfThree, append: true, headerRowIndex: headerRowIndex, startFrom: 7);
         writer.SaveAs(testFile);
 
         using var reader = new ExcelReader(testFile);
@@ -362,4 +362,23 @@ public class WriterTests
         for (int i = 0; i < readArray.Length; i++)
             Assert.Equal(ArrayOfThree[i], readArray[i]);
     }
+    
+    [Fact]
+    public void WriteWithStartFrom()
+    {
+        var testFile = Path.GetRandomFileName();
+        testFile = Path.ChangeExtension(testFile, "xlsx");
+
+        const string worksheetName = "Test";
+        using var writer = new ExcelWriter(testFile);
+        writer.Write(ArrayOfThree, worksheetName);
+        writer.Write(ListOfTwo, worksheetName, startFrom: (uint)(ArrayOfThree.Length + 3));
+        writer.SaveAs(testFile);
+
+        using var reader = new ExcelReader(testFile);
+        var readArray = reader.Read<Test>(worksheetName).ToArray();
+        Assert.Equal(6, readArray.Length);
+        
+        File.Delete(testFile);
+    }
 }