How to read an Excel file using C#

By: Rajesh P.S.

The following program demonstrates the process of opening an existing Excel spreadsheet in C# by using the COM interop capability within the .NET Framework. Additionally, the program showcases how to identify and retrieve Named Ranges within Excel, as well as how to determine the range of occupied cells (Used area) within an Excel sheet.

By utilizing the .NET Framework's COM interop capability, developers gain the ability to seamlessly integrate C# with Excel, enabling efficient interaction with Excel spreadsheets. Through this integration, the program opens an existing Excel spreadsheet, providing access to its data and functionalities.

Excel Library

To access the object model from Visual C# .NET, you have to add the Microsoft Excel 15.0 Object Library to you project.

Create a new project in your Visual Studio and add a Command Button to your C# Form.

How to use COM Interop to Create an Excel Spreadsheet

Form the following pictures you can find how to add Excel reference library in your project.

Select Add Reference dialogue from Project menu of your Visual Studio.

Select Microsoft Excel 15.0 Object Library of COM leftside menu and click OK button.

After import the reference library, we have to initialize the Excel application Object.

Excel.Application xlApp = new Excel.Workbook xlWorkBook ; Excel.Worksheet xlWorkSheet ; Excel.Range range ;

Next step is to open the Excel file and get the specified worksheet.

xlApp = new Excel.Application(); xlWorkBook = xlApp.Workbooks.Open(@"d:\csharp-Excel.xls", 0, true, 5, "", "", true, Microsoft.Office.Interop.Excel.XlPlatform.xlWindows, "\t", false, false, 0, true, 1, 0); xlWorkSheet = (Excel.Worksheet)xlWorkBook.Worksheets.get_Item(1);

After get the selcted worksheet, next step is to specify the used range in worksheet

How to specify a range in Excel sheet?

If you want to select a specific cell in Excel sheet, you can code like this.

Excel.Worksheet excelSheet = workbook.ActiveSheet; Excel.Range rng = (Excel.Range)excelSheet.Cells[10, 10];

Reading Named Ranges in Excel

Worksheet.get_Range Method

If you want to select multiple cell value from Excel sheet, you can code like this.

Excel.Worksheet excelSheet = workbook.ActiveSheet; Excel.Range rng = (Excel.Range) excelSheet.get_Range(excelSheet.Cells[1, 1], excelSheet.Cells[3,3]);

How to get the range of occupied cells in excel sheet

Find the last used row in Excel with C# , get the last filled excel row

For reading entire content of an Excel file in C#, we have to know how many cells used in the Excel file. In order to find the used range we use "UsedRange" property of xlWorkSheet . A used range includes any cell that has ever been used. It will return the last cell of used area.

Excel.Range range ; range = xlWorkSheet.UsedRange;

How to properly clean up Excel interop objects

How to create an Excel Document in C# , How to properly release Excel COM objects c#

Interop marshaling governs how data is passed in method arguments and return values between managed and unmanaged memory during calls. Most data types have common representations in both managed and unmanaged memory. The interop marshaler handles these types for you. Other types can be ambiguous or not represented at all in managed memory.

Marshal.ReleaseComObject (excelWB); Marshal.ReleaseComObject (excelApp);

It is important to note that every reference to an Excel COM object had to be set to null when you have finished with it, including Cells, Sheets, everything.

The Marshal class is in the System.Runtime.InteropServices namespace, so you should import the following namespace.

using System.Runtime.InteropServices;

Open and Read an Excel Spreadsheet Programmatically

Copy and paste the following source code in your C# project file

Full Source C#

using System; using System.Windows.Forms; using System.Runtime.InteropServices; using Excel = Microsoft.Office.Interop.Excel; namespace WindowsFormsApplication4 { public partial class Form1 : Form { public Form1() { InitializeComponent(); } private void button1_Click(object sender, EventArgs e) { Excel.Application xlApp ; Excel.Workbook xlWorkBook ; Excel.Worksheet xlWorkSheet ; Excel.Range range ; string str; int rCnt ; int cCnt ; int rw = 0; int cl = 0; xlApp = new Excel.Application(); xlWorkBook = xlApp.Workbooks.Open(@"d:\csharp-Excel.xls", 0, true, 5, "", "", true, Microsoft.Office.Interop.Excel.XlPlatform.xlWindows, "\t", false, false, 0, true, 1, 0); xlWorkSheet = (Excel.Worksheet)xlWorkBook.Worksheets.get_Item(1); range = xlWorkSheet.UsedRange; rw = range.Rows.Count; cl = range.Columns.Count; for (rCnt = 1; rCnt < = rw; rCnt++) { for (cCnt = 1; cCnt < = cl; cCnt++) { str = (string)(range.Cells[rCnt, cCnt] as Excel.Range).Value2; MessageBox.Show(str); } } xlWorkBook.Close(true, null, null); xlApp.Quit(); Marshal.ReleaseComObject(xlWorkSheet); Marshal.ReleaseComObject(xlWorkBook); Marshal.ReleaseComObject(xlApp); } } }

When you execute this C# source code the program read all used cells from Excel file.

Conclusion

By examining this program, developers can gain valuable insights into the process of opening an existing Excel spreadsheet in C# and perform operations such as locating Named Ranges and obtaining the Used area within the sheet. These capabilities enhance the integration between C# and Excel, enabling developers to use Excel's powerful features within their C# applications.

Next > How to programmatically Add New Worksheets

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