Added polyfills and simplified preprocessor directives

src/MiniExcel.Core/Helpers/ExpandoHelper.cs

@@ -10,12 +10,7 @@ public static class ExpandoHelper
         for (int i = startCellIndex; i <= maxColumnIndex; i++)
         {
             var key = CellReferenceConverter.GetAlphabeticalIndex(i);
-#if NETCOREAPP2_0_OR_GREATER
             cell.TryAdd(key, null);
-#else
-            if (!cell.ContainsKey(key))
-                cell.Add(key, null);
-#endif
         }
 
         return cell;
@@ -26,12 +21,7 @@ public static class ExpandoHelper
         IDictionary<string, object?> cell = new ExpandoObject();
         foreach (var hr in headers)
         {
-#if NETCOREAPP2_0_OR_GREATER
             cell.TryAdd(hr.Value, null);
-#else
-            if (!cell.ContainsKey(hr.Value))
-                cell.Add(hr.Value, null);
-#endif
         }
 
         return cell;

src/MiniExcel.Core/Helpers/MiniExcelStreamWriter.cs

@@ -12,13 +12,12 @@ public async Task WriteAsync(string content, CancellationToken cancellationToken
     {
         if (!string.IsNullOrEmpty(content))
         {
-#if NET8_0_OR_GREATER
-            await _streamWriter.WriteAsync(content.AsMemory(), cancellationToken)
+#if NET
+            await _streamWriter.WriteAsync(content.AsMemory(), cancellationToken).ConfigureAwait(false);
 #else
             cancellationToken.ThrowIfCancellationRequested();
-            await _streamWriter.WriteAsync(content)
+            await _streamWriter.WriteAsync(content).ConfigureAwait(false);
 #endif
-                .ConfigureAwait(false);
         }
     }
 
@@ -33,7 +32,7 @@ public async Task<long> WriteAndFlushAsync(string content, CancellationToken can
     public async Task<long> FlushAndGetPositionAsync(CancellationToken cancellationToken = default)
     {
         await _streamWriter.FlushAsync(
-#if NET8_0_OR_GREATER
+#if NET
             cancellationToken
 #endif
         ).ConfigureAwait(false);

src/MiniExcel.Core/Helpers/Polyfills.cs

@@ -1,5 +1,7 @@
 using System.ComponentModel;
 using System.IO.Compression;
+using System.Runtime.InteropServices;
+using System.Xml.Linq;
 
 namespace MiniExcelLib.Core.Helpers;
 
@@ -9,10 +11,23 @@ in the other projects that require it so as to prevent the consumers' IDEs to be
 public static class Polyfills
 {
 #if NETSTANDARD2_0
-    [EditorBrowsable(EditorBrowsableState.Advanced)]
-    public static TValue? GetValueOrDefault<TKey, TValue>(this IDictionary<TKey, TValue> dictionary, TKey key, TValue? defaultValue = default)
+    extension<TKey, TValue>(IDictionary<TKey, TValue> dictionary)
     {
-        return dictionary.TryGetValue(key, out var value) ? value : defaultValue;
+        [EditorBrowsable(EditorBrowsableState.Advanced)]
+        public TValue? GetValueOrDefault(TKey key, TValue? defaultValue = default)
+        {
+            return dictionary.TryGetValue(key, out var value) ? value : defaultValue;
+        }
+
+        [EditorBrowsable(EditorBrowsableState.Advanced)]
+        public bool TryAdd(TKey key, TValue value)
+        {
+            if (dictionary.ContainsKey(key))
+                return false;
+
+            dictionary.Add(key, value);
+            return true;
+        }
     }
 
     [EditorBrowsable(EditorBrowsableState.Advanced)]
@@ -45,6 +60,50 @@ public static IEnumerable<TSource> ExceptBy<TSource, TKey>(this IEnumerable<TSou
             }
         }
     }
+
+    extension(Stream? stream)
+    {
+        [EditorBrowsable(EditorBrowsableState.Advanced)]
+        public ValueTask DisposeAsync()
+        {
+            if (stream is IAsyncDisposable asyncDisposable)
+                return asyncDisposable.DisposeAsync();
+
+            stream?.Dispose();
+            return default;
+        }
+
+        [EditorBrowsable(EditorBrowsableState.Advanced)]
+        public StreamConfiguredAsyncDisposable ConfigureAwait(bool continueOnCapturedContext) 
+            => new(stream, continueOnCapturedContext);
+    }
+
+    /// <summary>
+    /// This is a copy of the runtime's <see cref="ConfiguredAsyncDisposable" />, which we cannot instantiate directly for our needs
+    /// due to the constructor that initializes the object to eventually dispose being internal. 
+    /// </summary>
+    [StructLayout(LayoutKind.Auto)]
+    [EditorBrowsable(EditorBrowsableState.Advanced)]
+    public readonly struct StreamConfiguredAsyncDisposable : IDisposable
+    {
+        private readonly Stream? _source;
+        private readonly bool _continueOnCapturedContext;
+
+        internal StreamConfiguredAsyncDisposable(Stream? source, bool continueOnCapturedContext)
+        {
+            _source = source;
+            _continueOnCapturedContext = continueOnCapturedContext;
+        }
+
+        public ConfiguredValueTaskAwaitable DisposeAsync()
+        {
+            return _source is not null 
+                ? _source.DisposeAsync().ConfigureAwait(_continueOnCapturedContext) 
+                : default;
+        }
+
+        public void Dispose() => _source?.Dispose();
+    }
 #endif
 
 #if !NET10_0_OR_GREATER
@@ -58,6 +117,22 @@ public ValueTask<Stream> OpenAsync(CancellationToken cancellationToken = default
         }
     }
 
+    extension(XDocument doc)
+    {
+        [EditorBrowsable(EditorBrowsableState.Advanced)]
+        public static ValueTask<XDocument> LoadAsync(Stream stream, LoadOptions loadOptions, CancellationToken cancellationToken = default)
+        {
+            return new ValueTask<XDocument>(XDocument.Load(stream, loadOptions));
+        }
+
+        [EditorBrowsable(EditorBrowsableState.Advanced)]
+        public ValueTask SaveAsync(Stream stream, SaveOptions saveOptions, CancellationToken cancellationToken = default)
+        {
+            doc.Save(stream, saveOptions);
+            return default;
+        }
+    }
+
     extension(ZipArchive)
     {
         [EditorBrowsable(EditorBrowsableState.Advanced)]

src/MiniExcel.Core/MiniExcelDataReader.cs

@@ -294,17 +294,11 @@ public async Task CloseAsync()
         if (IsClosed)
             return;
 
-        if (_isAsyncSource)
-        {
+        if (_isAsyncSource) 
             await _asyncSource!.DisposeAsync().ConfigureAwait(false);
-        }
-        _source?.Dispose();
 
-#if NETCOREAPP3_0_OR_GREATER
+        _source?.Dispose();
         await _stream!.DisposeAsync().ConfigureAwait(false);
-#else
-        _stream.Dispose();
-#endif
 
         IsClosed = true;
     }

src/MiniExcel.Core/Reflection/MiniExcelMapper.cs

@@ -43,7 +43,7 @@
                     {
                         if (headersDic?.TryGetValue(alias, out var columnId) is true)
                         {
                             var columnName = keys[columnId];
                             item.TryGetValue(columnName, out var aliasItemValue);
 
                             if (aliasItemValue is not null)
@@ -62,7 +62,7 @@
                 }
                 else if (map.ExcelColumnName is not null && (headersDic?.TryGetValue(map.ExcelColumnName, out var columnId) is true))
                 {
                     var columnName = keys[columnId];
                     item.TryGetValue(columnName, out itemValue);
                 }
 
@@ -145,8 +145,8 @@
                 else
                     throw new InvalidCastException($"{vs} cannot be cast to DateTime");
             }
-            
-#if NET6_0_OR_GREATER
+
+#if NET
             else if (map.ExcludeNullableType == typeof(DateOnly))
             {
                 if (itemValue is DateOnly)

src/MiniExcel.Csv/Api/CsvExporter.cs

@@ -1,5 +1,3 @@
-using MiniExcelLib.Core;
-
 // ReSharper disable once CheckNamespace
 namespace MiniExcelLib.Csv;
 
@@ -20,7 +18,9 @@ public async Task<int> AppendAsync(string path, object value, bool printHeader =
             return rowsWritten.FirstOrDefault();
         }
 
-        using var stream = new FileStream(path, FileMode.Append, FileAccess.Write, FileShare.Read, 4096, FileOptions.SequentialScan);
+        var stream = new FileStream(path, FileMode.Append, FileAccess.Write, FileShare.Read, 4096, FileOptions.SequentialScan);
+        await using var disposableStream = stream.ConfigureAwait(false);
+
         return await AppendAsync(stream, value, configuration, progress, cancellationToken).ConfigureAwait(false);
     }
 
@@ -39,7 +39,9 @@ public async Task<int> AppendAsync(Stream stream, object value, CsvConfiguration
     public async Task<int[]> ExportAsync(string path, object value, bool printHeader = true, bool overwriteFile = false,
         CsvConfiguration? configuration = null, IProgress<int>? progress = null, CancellationToken cancellationToken = default)
     {
-        using var stream = overwriteFile ? File.Create(path) : new FileStream(path, FileMode.CreateNew);
+        var stream = overwriteFile ? File.Create(path) : new FileStream(path, FileMode.CreateNew);
+        await using var disposableStream = stream.ConfigureAwait(false);
+
         return await ExportAsync(stream, value, printHeader, configuration, progress, cancellationToken).ConfigureAwait(false);
     }
 

src/MiniExcel.Csv/Api/CsvImporter.cs

@@ -15,7 +15,8 @@ public async IAsyncEnumerable<T> QueryAsync<T>(string path, bool treatHeaderAsDa
         CsvConfiguration? configuration = null, [EnumeratorCancellation] CancellationToken cancellationToken = default)
         where T : class, new()
     {
-        using var stream = FileHelper.OpenSharedRead(path);
+        var stream = FileHelper.OpenSharedRead(path);
+        await using var disposableStream = stream.ConfigureAwait(false);
 
         var query = QueryAsync<T>(stream, treatHeaderAsData, configuration, cancellationToken);
 
@@ -38,7 +39,9 @@ public async IAsyncEnumerable<T> QueryAsync<T>(Stream stream, bool treatHeaderAs
     public async IAsyncEnumerable<dynamic> QueryAsync(string path, bool useHeaderRow = false, 
         CsvConfiguration? configuration = null, [EnumeratorCancellation] CancellationToken cancellationToken = default)
     {
-        using var stream = FileHelper.OpenSharedRead(path);
+        var stream = FileHelper.OpenSharedRead(path);
+        await using var disposableStream = stream.ConfigureAwait(false);
+
         await foreach (var item in QueryAsync(stream, useHeaderRow, configuration, cancellationToken).ConfigureAwait(false))
             yield return item;
     }
@@ -64,7 +67,9 @@ public async IAsyncEnumerable<dynamic> QueryAsync(Stream stream, bool useHeaderR
     public async Task<DataTable> QueryAsDataTableAsync(string path, bool useHeaderRow = true,
         CsvConfiguration? configuration = null, CancellationToken cancellationToken = default)
     {
-        using var stream = FileHelper.OpenSharedRead(path);
+        var stream = FileHelper.OpenSharedRead(path);
+        await using var disposableStream = stream.ConfigureAwait(false);
+
         return await QueryAsDataTableAsync(stream, useHeaderRow, configuration, cancellationToken).ConfigureAwait(false);
     }
 
@@ -127,7 +132,8 @@ public async Task<DataTable> QueryAsDataTableAsync(Stream stream, bool useHeader
     public async Task<ICollection<string>> GetColumnNamesAsync(string path, bool useHeaderRow = false,
         CsvConfiguration? configuration = null, CancellationToken cancellationToken = default)
     {
-        using var stream = FileHelper.OpenSharedRead(path);
+        var stream = FileHelper.OpenSharedRead(path);
+        await using var disposableStream = stream.ConfigureAwait(false);
         return await GetColumnNamesAsync(stream, useHeaderRow, configuration, cancellationToken).ConfigureAwait(false);
     }
 

src/MiniExcel.Csv/CsvReader.cs

@@ -33,7 +33,7 @@ internal CsvReader(Stream stream, IMiniExcelConfiguration? configuration)
 
         var rowIndex = 0;
         while (await reader.ReadLineAsync(
-#if NET7_0_OR_GREATER
+#if NET
             cancellationToken
 #endif
             ).ConfigureAwait(false) is { } row)
@@ -49,7 +49,7 @@ internal CsvReader(Stream stream, IMiniExcelConfiguration? configuration)
                 while (finalRow.Count(c => c == '"') % 2 != 0)
                 {
                     var nextPart = await reader.ReadLineAsync(
-#if NET7_0_OR_GREATER
+#if NET
                         cancellationToken
 #endif
                     ).ConfigureAwait(false);
@@ -159,12 +159,19 @@ private string[] Split(string row)
 
         //this code from S.O : https://stackoverflow.com/a/11365961/9131476
         return Regex.Split(row, $"[\t{_config.Seperator}](?=(?:[^\"]|\"[^\"]*\")*$)")
-            .Select(s => Regex.Replace(s.Replace("\"\"", "\""), "^\"|\"$", ""))
+            .Select(s => DoubleQuotesRegexImpl.Replace(s.Replace("\"\"", "\""), ""))
             .ToArray();
     }
 
     public void Dispose()
     {
-        ((Stream?)_stream)?.Dispose();
+        _stream?.Dispose();
     }
+#if NET
+    [GeneratedRegex("^\"|\"$")]
+    private static partial Regex DoubleQuotesRegex();
+    private static readonly Regex DoubleQuotesRegexImpl = DoubleQuotesRegex();
+#else
+    private static readonly Regex DoubleQuotesRegexImpl = new Regex("^\"|\"$",  RegexOptions.Compiled);
+#endif
 }