This sample show how to read data from excel file by using Microsoft.Jet.OLEDB.
More information about excel connectionstring see http://www.connectionstrings.com/excel
Let's sample code.
    Private Function ReadExcelFile(ByVal filePath As String, ByVal fileName As String) As DataSet
        '' Excel 2003
        Dim sConn As String = String.Format("Provider=Microsoft.Jet.OLEDB.4.0;Data Source={0}", filePath + fileName)
        sConn += ";Extended Properties=""Excel 8.0;HDR=Yes;IMEX=1;"""
        'Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\MyExcel.xls;Extended Properties="Excel 8.0;HDR=Yes;IMEX=1";
        Dim sSql As String = "SELECT * FROM [Sheet1$]"
'Select excel range  command
' Dim sSql As String = "SELECT * FROM [Sheet1$A1:D3]"
        Dim pFile As New FileInfo(fileName)
        If (pFile.Extension.ToLower() = ".xlsx") Then
            ' Excel 2007
            sConn = String.Format("Provider=Microsoft.ACE.OLEDB.12.0;Data Source={0}", filePath + fileName)
            sConn += ";Extended Properties=""Excel 12.0 Xml;HDR=YES;"""
        End If
        Dim ds As New DataSet
        Dim pConn As New OleDbConnection(sConn)
        Try
            pConn.Open()
            Dim pCmd As New OleDbCommand()
            pCmd.Connection = pConn
            pCmd.CommandText = sSql
            Dim pAdp As New OleDbDataAdapter()
            pAdp.SelectCommand = pCmd
            pAdp.Fill(ds)
        Catch ex As Exception
            Return Nothing
        Finally
            pConn.Close()
        End Try
        Return ds
    End Function
Note
If found error Could not find installable ISAM that mean your connectionstring was wrong.

