Make use of dynamic columns when generating sheet by IDataReader to c…

…hange column names & widths

src/MiniExcel/OpenXml/ExcelOpenXmlSheetWriter.cs

@@ -609,17 +609,26 @@ private void GenerateSheetByIDataReader(MiniExcelStreamWriter writer, IDataReade
                     writer.Write("                              />"); // end of code will be replaced
                 }
 
+                var props = new List<ExcelColumnInfo>();
+                for (var i = 0; i < reader.FieldCount; i++)
+                {
+                    var columnName = reader.GetName(i);
+                    var prop = GetColumnInfosForIDataReader(columnName);
+                    props.Add(prop);
+                }
+
+                WriteColumnsWidths(writer, props);
+
                 writer.Write("<x:sheetData>");
                 int fieldCount = reader.FieldCount;
                 if (_printHeader)
                 {
                     writer.Write($"<x:row r=\"{yIndex}\">");
                     xIndex = xy.Item1;
-                    for (int i = 0; i < fieldCount; i++)
+                    foreach (var p in props)
                     {
                         var r = ExcelOpenXmlUtils.ConvertXyToCell(xIndex, yIndex);
-                        var columnName = reader.GetName(i);
-                        WriteC(writer, r, columnName);
+                        WriteC(writer, r, columnName: p.ExcelColumnName);
                         xIndex++;
                     }
                     writer.Write($"</x:row>");
@@ -653,6 +662,54 @@ private void GenerateSheetByIDataReader(MiniExcelStreamWriter writer, IDataReade
             }
         }
 
+        private ExcelColumnInfo GetColumnInfosForIDataReader(string columnName)
+        {
+            var prop = new ExcelColumnInfo
+            {
+                ExcelColumnName = columnName,
+                Key = columnName
+            };
+
+            if (_configuration.DynamicColumns == null || _configuration.DynamicColumns.Length <= 0) 
+                return prop;
+
+            var dynamicColumn = _configuration.DynamicColumns.SingleOrDefault(_ => _.Key == columnName);
+            if (dynamicColumn == null || dynamicColumn.Ignore)
+            {
+                return prop;
+            }
+
+            prop.Nullable = true;
+            //prop.ExcludeNullableType = item2[key]?.GetType();
+            if (dynamicColumn.Format != null)
+                prop.ExcelFormat = dynamicColumn.Format;
+            if (dynamicColumn.Aliases != null)
+                prop.ExcelColumnAliases = dynamicColumn.Aliases;
+            if (dynamicColumn.IndexName != null)
+                prop.ExcelIndexName = dynamicColumn.IndexName;
+            prop.ExcelColumnIndex = dynamicColumn.Index;
+            if (dynamicColumn.Name != null)
+                prop.ExcelColumnName = dynamicColumn.Name;
+            prop.ExcelColumnWidth = dynamicColumn.Width;
+
+            return prop;
+        }
+
+        private static void WriteColumnsWidths(MiniExcelStreamWriter writer, IEnumerable<ExcelColumnInfo> props)
+        {
+            var ecwProps = props.Where(x => x?.ExcelColumnWidth != null).ToList();
+            if (ecwProps.Count <= 0)
+                return;
+            writer.Write($@"<x:cols>");
+            foreach (var p in ecwProps)
+            {
+                writer.Write(
+                    $@"<x:col min=""{p.ExcelColumnIndex + 1}"" max=""{p.ExcelColumnIndex + 1}"" width=""{p.ExcelColumnWidth}"" customWidth=""1"" />");
+            }
+
+            writer.Write($@"</x:cols>");
+        }
+
         private static void WriteC(MiniExcelStreamWriter writer, string r, string columnName)
         {
             writer.Write($"<x:c r=\"{r}\" t=\"str\" s=\"1\">");

tests/MiniExcelTests/MiniExcelOpenXmlTests.cs

@@ -1197,5 +1197,57 @@ public void SharedStringNoCacheTest()
             output.WriteLine("elapsedMilliseconds: " + stopWatch.ElapsedMilliseconds);
             stopWatch.Stop();
         }
+
+        [Fact]
+        public void DynamicColumnsConfigurationIsUsedWhenCreatingExcelUsingIDataReader()
+        {
+            var path = Path.Combine(Path.GetTempPath(), $"{Guid.NewGuid()}.xlsx");
+            var table = new DataTable();
+            {
+                table.Columns.Add("Column1", typeof(string));
+                table.Columns.Add("Column2", typeof(int));
+                table.Rows.Add("MiniExcel", 1);
+                table.Rows.Add("Github", 2);
+            }
+
+            var configuration = new OpenXmlConfiguration
+            {
+                DynamicColumns = new[]
+                {
+                    new DynamicExcelColumn("Column1")
+                    {
+                        Name = "Name of something",
+                        Index = 0,
+                        Width = 150
+                    },
+                    new DynamicExcelColumn("Column2")
+                    {
+                        Name = "Its value",
+                        Index = 1,
+                        Width = 150
+                    }
+                }
+            };
+            var reader = table.CreateDataReader();
+
+            MiniExcel.SaveAs(path, reader, configuration: configuration);
+
+            using (var stream = File.OpenRead(path))
+            {
+                var rows = stream.Query(useHeaderRow: true)
+                    .Select(x => (IDictionary<string,object>)x)
+                    .ToList();
+
+                Assert.Contains("Name of something", rows[0]);
+                Assert.Contains("Its value", rows[0]);
+                Assert.Contains("Name of something", rows[1]);
+                Assert.Contains("Its value", rows[1]);
+
+                Assert.Equal("MiniExcel", rows[0]["Name of something"]);
+                Assert.Equal(1D, rows[0]["Its value"]);
+                Assert.Equal("Github", rows[1]["Name of something"]);
+                Assert.Equal(2D, rows[1]["Its value"]);
+            }
+        }
     }
 }