Initial commit of the ClosedXML library

Establishes the foundational structure, core Excel functionality, and tooling.

- Implements base components for cells, ranges, columns, and rows.
- Integrates a custom calculation engine with a wide range of Excel functions.
- Adds comprehensive support for styling, conditional formatting, data validation, comments, pictures, and charts.
- Configures build setup, project metadata (NuGet), and developer guidelines.
- Includes editor and Git attributes for consistent code style and line endings.

ClosedXML_Tests/OleDb/OleDbTests.cs

@@ -0,0 +1,120 @@
+#if !APPVEYOR && _NETFRAMEWORK_
+using ClosedXML.Excel;
+using ClosedXML_Tests.Utils;
+using NUnit.Framework;
+using System;
+using System.Collections.Generic;
+using System.Data;
+using System.Data.OleDb;
+using System.IO;
+using System.Linq;
+
+namespace ClosedXML_Tests.OleDb
+{
+    [TestFixture]
+    public class OleDbTests
+    {
+        [Test]
+        public void TestOleDbValues()
+        {
+            using (var tf = new TemporaryFile(CreateTestFile()))
+            {
+                Console.Write("Using temporary file\t{0}", tf.Path);
+                var connectionString = string.Format(@"Provider=Microsoft.ACE.OLEDB.12.0;Data Source={0};Extended Properties='Excel 12.0 Xml;HDR=YES;IMEX=1';", tf.Path);
+                using (var connection = new OleDbConnection(connectionString))
+                {
+                    // Install driver from https://www.microsoft.com/en-za/download/details.aspx?id=13255 if required
+                    // Also check that test runner is running under correct architecture:
+                    connection.Open();
+                    using (var command = new OleDbCommand("select * from [Sheet1$]", connection))
+                    using (var dataAdapter = new OleDbDataAdapter())
+                    {
+                        dataAdapter.SelectCommand = command;
+                        var dt = new DataTable();
+                        dataAdapter.Fill(dt);
+
+                        Assert.AreEqual("Base", dt.Columns[0].ColumnName);
+                        Assert.AreEqual("Ref", dt.Columns[1].ColumnName);
+
+                        Assert.AreEqual(2, dt.Rows.Count);
+
+                        Assert.AreEqual(42, dt.Rows.Cast<DataRow>().First()[0]);
+                        Assert.AreEqual(42, dt.Rows.Cast<DataRow>().First()[1]);
+
+                        Assert.AreEqual(41, dt.Rows.Cast<DataRow>().Last()[0]);
+                        Assert.AreEqual(41, dt.Rows.Cast<DataRow>().Last()[1]);
+                    }
+
+                    using (var command = new OleDbCommand("select * from [Sheet2$]", connection))
+                    using (var dataAdapter = new OleDbDataAdapter())
+                    {
+                        dataAdapter.SelectCommand = command;
+                        var dt = new DataTable();
+                        dataAdapter.Fill(dt);
+
+                        Assert.AreEqual("Ref1", dt.Columns[0].ColumnName);
+                        Assert.AreEqual("Ref2", dt.Columns[1].ColumnName);
+                        Assert.AreEqual("Sum", dt.Columns[2].ColumnName);
+                        Assert.AreEqual("SumRef", dt.Columns[3].ColumnName);
+
+                        var expected = new Dictionary<string, double>()
+                        {
+                            {"Ref1", 42 },
+                            {"Ref2", 41 },
+                            {"Sum", 83 },
+                            {"SumRef", 83 },
+                        };
+
+                        foreach (var col in dt.Columns.Cast<DataColumn>())
+                            foreach (var row in dt.Rows.Cast<DataRow>())
+                            {
+                                Assert.AreEqual(expected[col.ColumnName], row[col]);
+                            }
+
+                        Assert.AreEqual(2, dt.Rows.Count);
+                    }
+
+                    connection.Close();
+                }
+            }
+        }
+
+        private string CreateTestFile()
+        {
+            using (var wb = new XLWorkbook())
+            {
+                var ws = wb.AddWorksheet("Sheet1");
+                ws.Cell("A1").Value = "Base";
+                ws.Cell("B1").Value = "Ref";
+
+                ws.Cell("A2").Value = 42;
+                ws.Cell("A3").Value = 41;
+
+                ws.Cell("B2").FormulaA1 = "=A2";
+                ws.Cell("B3").FormulaA1 = "=A3";
+
+                ws = wb.AddWorksheet("Sheet2");
+                ws.Cell("A1").Value = "Ref1";
+                ws.Cell("B1").Value = "Ref2";
+                ws.Cell("C1").Value = "Sum";
+                ws.Cell("D1").Value = "SumRef";
+
+                ws.Cell("A2").FormulaA1 = "=Sheet1!A2";
+                ws.Cell("B2").FormulaA1 = "=Sheet1!A3";
+                ws.Cell("C2").FormulaA1 = "=SUM(A2:B2)";
+                ws.Cell("D2").FormulaA1 = "=SUM(Sheet1!A2:Sheet1!A3)";
+
+                ws.Cell("A3").FormulaA1 = "=Sheet1!B2";
+                ws.Cell("B3").FormulaA1 = "=Sheet1!B3";
+                ws.Cell("C3").FormulaA1 = "=SUM(A3:B3)";
+                ws.Cell("D3").FormulaA1 = "=SUM(Sheet1!B2:Sheet1!B3)";
+
+                var path = Path.ChangeExtension(Path.GetTempFileName(), "xlsx");
+                wb.SaveAs(path, true, true);
+
+                return path;
+            }
+        }
+    }
+}
+#endif