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How to: Get Data from Multiple Workbooks using One OleDbConnection?

, 3 Jan 2014
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This tip shows how to get data from multiple workbooks using one OledbConnection.

Introduction

Several times I've seen questions similar to:

  • How to get data into datatable from multiple Excel sources using ADO.NET?
  • How to join data from multiple workbooks using single OleDbConnection object?
  • How to read data from multiple workbooks using into a single Datatable object?

This tip shows how to achieve that.

On the other side, sometimes we need to compare data stored in 2 different Excel files. The most popular solution for that is to loop through the data in both files using Interop[^].

The pseudo-code is as follows:

For each row in FirstFile
    For each row in SecondFile
        'comparison is coming here 
    Next
Next 

Definitely it is an inefficient way! So, what to do? In that case, I would strongly recommend to use ADO.NET (OleDb)!

Background

There are two interesting articles on MSDN about using ADO.NET with Excel (Office) application:

  1. Accessing MS Office Data from .NET applications (VB.NET)
  2. How to use ADO.NET to retrieve and modify records in an Excel workbook (VB.NET)

This is not a complete list of useful articles, of course, but the most recommended.

You'll find many useful articles in the CodeProject Knowledge Base too. But nowhere have I found a way to compare data or join/read data from multiple Excel files using single OleDb connection.

Idea

The main idea is to use IN clause. OleDb provider for MS JET database engine supports IN clause in the same way as Microsoft Access database does.

SELECT *
FROM [Sheet1$] IN 'D:\SampleFile.xls' 'Excel 8.0;'

Using the Code

Below is the complete C# and VB.NET code for ConsoleApplication.

using System;
using System.Data;
using System.Data.OleDb;
using System.Collections.Generic;
using System.Text;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
        OleDbConnection oConn = null;
        OleDbCommand oComm = null;
        OleDbDataReader oRdr = null;
        DataTable oTbl = null;
        String sFirstFile = String.Empty;
        String sSecondFile= String.Empty;
        String sConnString = String.Empty;
        String sCommand = String.Empty;
        try
            {
            sFirstFile = @"D:\Fruits1.xls";
            sSecondFile = @"D:\Fruits2.xls";
            sConnString = @"Provider=Microsoft.Jet.OLEDB.4.0;
            Data Source=" + sFirstFile + ";Extended Properties='Excel 8.0;HDR=Yes';";
            oConn = new OleDbConnection(sConnString);
            oConn.Open();
            sCommand  = @"SELECT NameOfFruit" + Environment.NewLine +
                        "FROM [Fruits$]" + Environment.NewLine +
                        "UNION ALL" + Environment.NewLine +
                        "SELECT NameOfFruit" + Environment.NewLine + 
                        "FROM [Fruits$] IN '" + sSecondFile + "' 'Excel 8.0;';";
            oComm = new OleDbCommand(sCommand, oConn);
            oRdr = oComm.ExecuteReader();
            oTbl = new DataTable();
            oTbl.Load(oRdr);

            foreach (DataRow row in oTbl.Rows)
                {
                Console.WriteLine(row["NameOfFruit"].ToString());
                }
            
            Console.ReadKey();
            }
        catch (Exception ex)
            {
                Console.WriteLine(ex.Message);
                Console.ReadKey();
            }
        finally
            {
            if (oRdr!=null) oRdr.Close();
            oRdr = null;
            if (oTbl !=null) oTbl.Dispose();
            oComm.Dispose();
            oConn.Close();
            oConn.Dispose();
            }
        }
    }
}
Module Module1

    Sub Main()

        Dim oConn As OleDb.OleDbConnection = Nothing
        Dim oComm As OleDb.OleDbCommand = Nothing
        Dim oRdr As OleDb.OleDbDataReader = Nothing
        Dim oTbl As Data.DataTable = Nothing
        Dim sFirstFile As String = String.Empty
        Dim sSecondFile As String = String.Empty

        Try
            sFirstFile = "D:\Fruits1.xls"
            sSecondFile = "D:\Fruits2.xls"
            oConn = New OleDb.OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;_
            Data Source=" & sFirstFile & ";Extended Properties='Excel 8.0;HDR=Yes';")
            oConn.Open()
            oComm = New OleDb.OleDbCommand("SELECT NameOfFruit" & vbCr & _
                                            "FROM [Fruits$]" & vbCr & _
                                            "UNION ALL" & vbCr & _
                                            "SELECT NameOfFruit" & vbCr & _
                                            "FROM [Fruits$] IN '" & _
                                            sSecondFile & "' 'Excel 8.0;';", oConn)
            oRdr = oComm.ExecuteReader()
            oTbl = New DataTable
            oTbl.Load(oRdr)

            For Each row As DataRow In oTbl.Rows
                Console.WriteLine(row.Item("NameOfFruit").ToString())
            Next

            Console.ReadKey()

        Catch ex As Exception
            Console.WriteLine(ex.Message)
            Console.ReadKey()
        Finally
            If Not oRdr Is Nothing Then oRdr.Close()
            oRdr = Nothing
            If Not oTbl Is Nothing Then oTbl.Dispose()
            oComm.Dispose()
            oConn.Close()
            oConn.Dispose()
        End Try


    End Sub

End Module

As you can see, there is only one OleDbConnection and one OleDbCommand to retrieve data from 2 different workbooks.

How to Compare Data Stored in Different Workbooks?

Using the same method as above but with different query:

SELECT NameOfFruit
FROM [Fruits$]
WHERE NameOfFruit NOT IN (SELECT NameOfFruit _
FROM [Fruits$] IN 'D\Data\Fruits2.xls' 'Excel 8.0;');

Using the above query, you'll fetch unique data from Fruit1.xls file. Equal data are ignored.

Points of Interest

Using OleDb to fetch data or compare data stored in two different workbooks is:

  1. faster than using Interop
  2. more universal (does not require installation of Microsoft Excel)

History

  • 2014/01/03 - First version (misspelling corrected)
  • 2013/12/27 - First version

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

About the Author

Maciej Los
Team Leader
Poland Poland
I'm a lawyer, teacher/trainer and author of VBA programming book (only polish version). Programming is my hobby!
  1. VB/VBA/VB.NET
  2. C#
  3. C++
  4. SQL
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Comments and Discussions

 
QuestionHelpful Tip Pinmemberkarthy Udhaykumar22-May-14 7:28 
AnswerRe: Helpful Tip PinmvpMaciej Los22-May-14 7:36 

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