Excel is such a powerful tool that almost all companies make extensive use of it for analyzing data. Moreover, the internet is not as it was 10 years ago. Almost all pages that are out there on the internet are dynamic ones, that is, interacts with a database in backend to produce results. Sometimes, data that are displayed, if made available on in an Excel file, proper analysis of the data often helps in making more accurate decisions by using Excel features. In this tutorial, we will learn how to interact with Excel files, both reading and writing. You can download Excel Reports Example ASP.NET Project associated with this tutorial.

For the purpose of this tutorial, an Excel sheet had been prepared that holds record of students and their respective marks in subjects. Please note that these records are fictitious and had been input randomly.

Interacting with Excel

Fortunately, there are COM objects that are available to interact with the Excel file. Also, we can make use of the OleDB class to treat the Excel file as a simple table. In this way, we can fire SQL queries to the Excel file so that we can retrieve data from the sheets. An analogy can be made to a database. The Excel Workbook is considered as the Database while the Sheets are considered as tables. Microsoft Excel 11.0 Object Library should be added as Reference to get the features for interacting with Excel.

The Excel file is then added to the DataSource folder in ASAP.NET to be interacted with. To connect to a certain database, a connection string is needed. The same thing applies for Excel. The following is a key added in the Web.Config file for future reference.

<add name="ExcelConnection" connectionString="Provider=Microsoft.Jet.Oledb.4.0;Data Source=|DataDirectory|\SchoolMgt.xls;Extended Properties=Excel 8.0"/>

Note that our Excel file which contains the necessary data will be SchoolMgt.xls, as written in the connection string.

Reading data from Excel sheets

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Let us build an interface for getting data from the Excel file.

It is important to import the following:

Imports System.Data.OleDb
Imports System.Data

The following code creates the connection and builds the query based on the selected table.

Protected Sub btnSearch_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnSearch.Click
Try
            Dim strExcelConn As String = System.Configuration.ConfigurationManager.ConnectionStrings.Item("ExcelConnection").ToString()
            Dim dbConn As New OleDbConnection(strExcelConn)
            Dim strSQL As String
 
            strSQL = "SELECT * FROM [" & cmbSheets.SelectedItem.ToString() & "$]"
 
            dbConn.Open()
 
            Dim cmd As New OleDbCommand(strSQL, dbConn)
            Dim dsExcel As New DataSet
            Dim daExcel As New OleDbDataAdapter(cmd)
 
            daExcel.Fill(dsExcel)
 
            dgResults.DataSource = dsExcel
            dgResults.DataBind()
        Catch ex As Exception
            Throw ex
        End Try
End Sub

Please note that the table name in the SELECT query should be in the format [TableName$], which the square brackets and the dollar sign at the end.

Playing with SELECT statements

As you have guessed, the Excel file has turned out to be a normal database. The transparency that the OleDB connection had made is exceptional. Also, note that the first row is taken to contain field names for the columns.

Now, let us get the marks of the students in Mathematics, Geography and Total, sorted in Descending order.

Protected Sub btnGenerateReport_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnGenerateReport.Click
Try
 
Dim strExcelConn As String = System.Configuration.ConfigurationManager.ConnectionStrings.Item("ExcelConnection").ToString()
Dim dbConn As New OleDbConnection(strExcelConn)
Dim strSQL As String
 
strSQL = "SELECT S.StudentId, S.StudentName, M.Marks, G.Marks, (M.Marks+G.Marks) AS Total "& _
                     "FROM [Students$] S, [Mathematics$] M, [Geography$] G "& _
                     "WHERE(S.StudentId = M.StudentId And S.StudentId = G.StudentId) " & _
                     "ORDER BY (M.Marks+G.Marks) DESC"
dbConn.Open()
 
Dim cmd As New OleDbCommand(strSQL, dbConn)
Dim dsExcel As New DataSet
Dim daExcel As New OleDbDataAdapter(cmd)
 
daExcel.Fill(dsExcel)
 
dgReports.DataSource = dsExcel
dgReports.DataBind()
 
Catch ex As Exception
Throw ex
End Try
End Sub

Generating Excel Reports

Two ways for generating Excel report will be discussed in this tutorial. The first one is using the "Response" class and the second one by manipulating the Excel objects that "Microsoft Excel 11.0" Objects provide.

The following piece of code illustrates how this is done

    Protected Sub btnToExcelByResponse_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnToExcelByResponse.Click
        '   Variables declaration
        Dim dsExport As New DataSet()
        Dim tw As New System.IO.StringWriter()
        Dim hw As New System.Web.UI.HtmlTextWriter(tw)
        Dim dgGrid As New DataGrid()
 
        dgGrid.DataSource = getData()
 
        '   Report Header
        hw.WriteLine("<b><u><font size='5'> Student Marking Report </font></u></b>")
 
        '   Get the HTML for the control.
        dgGrid.HeaderStyle.Font.Bold = True
        dgGrid.DataBind()
        dgGrid.RenderControl(hw)
 
        '   Write the HTML back to the browser.
        Response.ContentType = "application/vnd.ms-excel"
        Me.EnableViewState = False
        Response.Write(tw.ToString())
        Response.End()
    End Sub

• First, we create the dataset that will hold the records. Then, a StringWriter object (tw) is also created along with an HtmlTextWriter (hw) which takes as parameter the text writer object. They are important for rendering purposes; i.e. html tags can be applied like bold, italic etc. to the resulting Excel report.

• Also, a datagrid object which will store the dataset of records.

• Note that function getData() in the code snippet only contains the codes in the previous example which returns a dataset of records.

• hw.WriteLine("<b><u><font size='5'> Student Marking Report </font></u></b>") shows that you can also combine HTML codes with the output for proper display. In our example, the font size will be 5, underlined and bold.

• dgGrid.RenderControl(hw) renders the HTML object with the data that the datagrid contains. The result is normally formatted in a tabular format.

• Response.ContentType = "application/vnd.ms-excel" makes the Reponse object output to Excel.

• Response.Write(tw.ToString()) outputs the formatted object to Excel.

The second way for generating Excel reports from ASP.NET is to use the Microsoft Excel 11.0 Objects. This method offers more fallibility in terms of manipulating the features that Excel provides and formatting the report.

The following code snippet makes use of the various Excel objects that Excel provides to generate the report.

Imports System.Reflection
Imports Excel = Microsoft.Office.Interop.Excel
 
    Protected Sub btnToExcelByObjects_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnToExcelByObjects.Click
        Try
            Dim xlWorkBook As Excel.Workbook
            Dim xlWorkSheet As Excel.Worksheet
 
            xlWorkBook = New Excel.Application().Workbooks.Add(Missing.Value)
            xlWorkBook.Application.Visible = True
            xlWorkSheet = xlWorkBook.ActiveSheet
 
            '   Gets the dataset containing the data
            Dim dsData As DataSet = getData()
            Dim i As Integer = 2
 
            '   Outputting the fieldnames in pink bold color
            xlWorkSheet.Cells(1, 1) = "Student ID"
            xlWorkSheet.Cells(1, 2) = "Student Name"
            xlWorkSheet.Cells(1, 3) = "Mathematics"
            xlWorkSheet.Cells(1, 4) = "Geography"
            xlWorkSheet.Cells(1, 5) = "Total"
 
            xlWorkSheet.Range("$A1:$E1").Font.ColorIndex = Excel.Constants.xlColor1
            xlWorkSheet.Range("$A1:$E1").Font.Bold = True
 
            '   Outputting the data
            For Each dr As DataRow In dsData.Tables(0).Rows
                xlWorkSheet.Cells(i, 1) = dr(0)
                xlWorkSheet.Cells(i, 2) = dr(1)
                xlWorkSheet.Cells(i, 3) = dr(2)
                xlWorkSheet.Cells(i, 4) = dr(3)
 
                '   Building the formula for calculating the sum
                xlWorkSheet.Cells(i, 5).Formula = "=SUM($C{0}:$D{0})".Replace("{0}", i.ToString())
 
                '   Going to the next row
                i = i + 1
            Next
 
            '   Auto fit the columns
            xlWorkSheet.Columns.AutoFit()
 
            '   Generating the graph
            Dim chart As Excel.Chart
            chart = xlWorkBook.Charts.Add()
 
            With chart
                .ChartType = Excel.XlChartType.xlColumnClustered
                .SetSourceData(xlWorkSheet.Range("A1:E11"), 2)
 
                .HasTitle = True
                .ChartTitle.Characters.Text = "Students' marks"
 
                .Axes(1, Excel.XlAxisGroup.xlPrimary).HasTitle = True
                .Axes(1, Excel.XlAxisGroup.xlPrimary).AxisTitle.Characters.Text = "Students"
                .Axes(2, Excel.XlAxisGroup.xlPrimary).HasTitle = True
                .Axes(2, Excel.XlAxisGroup.xlPrimary).AxisTitle.Characters.Text = "Marks"
            End With
        Catch ex As Exception
            Throw ex
        End Try
    End Sub

An Excel workbook is first created. Then the active sheet is accessed by xlWorkSheet = xlWorkBook.ActiveSheet. After that, we get the data into the dataset, ready to be processed. Using the Font property, the title is displayed in Pink bold colour. Note how the Formula that Excel provides is properly used to calculate the SUM of the marks for each student xlWorkSheet.Cells(i, 5).Formula = "=SUM($C{0}:$D{0})".Replace("{0}", i.ToString()).

A chart is also generated using the objects. The x-axis consists of the names and id of each student. The y-axis, the marks for the different students. The chart is always handy for analysis of data.

Summary

In this tutorial, you learned how to read data from Excel, generate report using the Response objects and to play with the Microsoft Excel 11.0 objects provided. Indeed, it is impossible to cover all features in this tutorial but many important techniques were covered to help you down the line. It is up to you to be creative and adapt the techniques to your scenarios.

Going professional with NativeExcel for .NET

Excel is powerful tool, but in real world development you rarely have Microsoft Office installed on your web server. There is no Excel on shared hosting and obtaining Office license for dedicated server is possible, but also pretty expensive. Fortunately, there is pure .NET component named Native Excel for .NET that creates or modifies Excel documents on the fly. For just $120 for single license you can use it on unlimited number of web sites and servers (source code available too). It is easier to distribute application since you work with simple assembly written in C#, instead of COM Excel object. Best of all, you don't need to learn anything new because objects and properties are identical to Excel's, so if you understood this tutorial you are already expert for NativeExcel too :).

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