c# programming. importing and exporting data from excel.

Concept

1. User browses and selects an Excel Workbook.

2. User selects whether Header row is present in Excel Sheet or not using radio buttons.

3. User uploads the Excel Workbook

4. Uploaded File is read by the application into a DataSet and displayed on the web page using GridView Control.

5. GridView has paging enabled so that user can view the records easily.

 code snippet:

Since there Excel 97-2003 and Excel 2007 use different providers I have placed two connection strings keys in the Web.Config. 

connectionStrings>

  <add name ="Excel03ConString"

       connectionString="Provider=Microsoft.Jet.OLEDB.4.0;Data Source={0};

                         Extended Properties='Excel 8.0;HDR={1}'"/>

  <add name ="Excel07ConString"

       connectionString="Provider=Microsoft.ACE.OLEDB.12.0;Data Source={0};

                         Extended Properties='Excel 8.0;HDR={1}'"/>

</connectionStrings>

You will notice above there are two connection strings one for Excel 97 – 2003 format which uses Microsoft Jet driver and another one is for Excel 2007 format which uses Microsoft Ace driver.

I have used Placeholders for Data Source {0} and the HDR {1} property so that I can easily replace fill it in the front end based on the Excel File Selected and the Headers property selected by the user through the checkbox respectivey

Front End design

The front end design of the web page contains a FileUpload Control, a Button which will be used to upload the Excel File, RadioButtonList for the user to select whether headers are present or not by default Yes is selected and finally the GridView control in which I have set AllowPaging property to true.

 code snippet.

<asp:FileUpload ID="FileUpload1" runat="server" />

<asp:Button ID="btnUpload" runat="server" Text="Upload"

            OnClick="btnUpload_Click" />

<br />

<asp:Label ID="Label1" runat="server" Text="Has Header ?" />

<asp:RadioButtonList ID="rbHDR" runat="server">

    <asp:ListItem Text = "Yes" Value = "Yes" Selected = "True" >

    </asp:ListItem>

    <asp:ListItem Text = "No" Value = "No"></asp:ListItem>

</asp:RadioButtonList>

<asp:GridView ID="GridView1" runat="server"

OnPageIndexChanging = "PageIndexChanging" AllowPaging = "true">

</asp:GridView>

Uploading and Reading the Excel Sheet

Next comes the part to upload the file and reading it. As you will notice in the aspx I have added OnClick event handler to the Upload button which will be triggered when the upload button is clicked

When the upload button is clicked the uploaded File is saved to a Folder whose path is defined in the App Settings section in the Web.Config using the following key

code snippet;

<appSettings>

  <add key ="FolderPath" value ="Files/"/>

</appSettings >

Once the File is saved in the folder the Import_To_Grid method is called up which is described later. Below is the code snippet for the Upload button event handler

C# code snippet

protected void btnUpload_Click(object sender, EventArgs e)

{

    if (FileUpload1.HasFile)

    {

        string FileName = Path.GetFileName(FileUpload1.PostedFile.FileName);

        string Extension = Path.GetExtension(FileUpload1.PostedFile.FileName);

        string FolderPath = ConfigurationManager.AppSettings["FolderPath"];

        string FilePath = Server.MapPath(FolderPath + FileName);

        FileUpload1.SaveAs(FilePath);

        Import_To_Grid(FilePath, Extension, rbHDR.SelectedItem.Text);

    }

}

Now the saved Excel file is read using OLEDB. Based on the extension I decide the driver to be used in order to read the excel file and also whether Excel will be read along with header row or not based on the RadioButtonList. All these values are filled in the placeholders of the connection string.

After that I read the schema of the Excel Workbook in order to find out the Sheet Name of the first sheet. Once I get that I fire a select query on the first Excel sheet and fill a datatable which is then passed to the GridView as data source. You can refer the complete function below

                     

C# code snippet

private void Import_To_Grid(string FilePath, string Extension, string isHDR)

{

    string conStr="";

    switch (Extension)

    {

        case ".xls": //Excel 97-03

            conStr = ConfigurationManager.ConnectionStrings["Excel03ConString"]

                     .ConnectionString;

            break;

        case ".xlsx": //Excel 07

            conStr = ConfigurationManager.ConnectionStrings["Excel07ConString"]

                      .ConnectionString;

            break;

    }

    conStr = String.Format(conStr, FilePath, isHDR);

    OleDbConnection connExcel = new OleDbConnection(conStr);

    OleDbCommand cmdExcel = new OleDbCommand();

    OleDbDataAdapter oda = new OleDbDataAdapter();

    DataTable dt = new DataTable();

    cmdExcel.Connection = connExcel;

    //Get the name of First Sheet

    connExcel.Open();

    DataTable dtExcelSchema;

    dtExcelSchema = connExcel.GetOleDbSchemaTable(OleDbSchemaGuid.Tables, null);

    string SheetName = dtExcelSchema.Rows[0]["TABLE_NAME"].ToString();

    connExcel.Close();

    //Read Data from First Sheet

    connExcel.Open();

    cmdExcel.CommandText = "SELECT * From [" + SheetName + "]";

    oda.SelectCommand = cmdExcel;

    oda.Fill(dt);

    connExcel.Close();

    //Bind Data to GridView

    GridView1.Caption = Path.GetFileName(FilePath);

    GridView1.DataSource = dt;

    GridView1.DataBind();

}

Pagination in GridView

Now in order to implement paging we will need to read the excel sheet each time and then rebind datatable to the GridView. Refer below

C# code snippet

protected void PageIndexChanging(object sender, GridViewPageEventArgs e)

{

    string FolderPath = ConfigurationManager.AppSettings["FolderPath"] ;

    string FileName = GridView1.Caption;

    string Extension = Path.GetExtension(FileName);

    string FilePath = Server.MapPath(FolderPath + FileName);

    Import_To_Grid(FilePath, Extension, rbHDR.SelectedItem.Text); 

    GridView1.PageIndex = e.NewPageIndex;

    GridView1.DataBind(); 

}