vb.net generalized write of data to excel - vb.net

Question

I need to create an excel file from scratch in VB.NET given a DataTable from asp.net.
I can do this for a specific file, but I don't know how to do it for a general database.
That is, where I use the "CREATE TABLE ..." I don't know how to tell it what types to use for the data in the table.
The DataTable is derived from a FoxPro database. (I don't know if that matters.)
I invoke the table similar to as follows:
<%
return_value = make_excel( sql_table, excel_filename)
%>
make_excel is defined as
Option Explicit On
'Option Strict On
Imports System
Imports System.Web
Imports System.Web.UI
Imports System.Web.UI.Page
Imports System.IO
Imports Microsoft.VisualBasic
Imports System.Diagnostics
Imports System.Data
Imports System.Data.OleDb
Public Class clsCommon
Inherits Page
' buncha other stuff defined in here.
Public Shared Function make_excel(ByVal sqlTable As DataTable, ByVal xls_fn As String) As Boolean
Dim conn As System.Data.OleDb.OleDbConnection
Dim ds As System.Data.DataSet
Dim cmd As New System.Data.OleDb.OleDbCommand()
conn = New System.Data.OleDb.OleDbConnection("provider=Microsoft.Jet.OLEDB.4.0;Data Source='" & xls_fn & "';Extended Properties=Excel 8.0;")
conn.Open()
cmd.Connection = conn
cmd.CommandText = "CREATE TABLE MyTable ( Admin char(20), first_name char(20));"
cmd.ExecuteNonQuery()
cmd.CommandText = "INSERT INTO MyTable ( Admin, first_name ) VALUES ('true', 'Bob')"
cmd.ExecuteNonQuery()
conn.Close()
Return True
End Function
End Class
What I need to be able to do is run through the values in sqlTable above, check their type and then build the sql to write them. Pointers?

Answer 1

Have you looked into the copyfromrecordset function? You'll need to do a bit of work and its a bit of a change of approach but it might be something you can look into. An MS article is available here (Sorry, the article is based around VBA, but it should help as a guide).

Answer 2

I have a solution to the problem. I'm not happy about it as a general solution, but it works well enough for the cases I'm currently dealing with.
In this solution, I create a template of the excel file that has the column headings I want to use. When I do the select in the forward code, I change the name of the fields as appropriate (or drop whatever fields I don't want).
Public Shared Function TestXL(ByVal resp As HttpResponse, ByVal sqlTable As DataTable, ByVal xls_template_fn As String, ByVal xls_fn As String) As Boolean
Dim conn As System.Data.OleDb.OleDbConnection
Dim ds As System.Data.DataSet
Dim cmd As New System.Data.OleDb.OleDbCommand()
Dim r As DataRow
Dim c As DataColumn
Dim i As Integer
Dim sql As String
dim str as string
If File.Exists(xls_template_fn) Then
try
If File.Exists(xls_fn) Then
File.Delete(xls_fn)
Else
File.Copy(xls_template_fn, xls_fn)
End If
catch ex1 as Exception
File.Copy(xls_template_fn, xls_fn)
End Try
Else
resp.Write("Unable to locate template file: " & xls_template_fn)
Return False
End If
conn = New System.Data.OleDb.OleDbConnection("provider=Microsoft.Jet.OLEDB.4.0;Data Source='" & xls_fn & "';Extended Properties=Excel 8.0;")
conn.Open()
cmd.Connection = conn
cmd.CommandText = sql
For Each r In sqlTable.Rows
sql = "INSERT INTO MyTable ("
For i = 0 To sqlTable.Columns.Count - 1
sql = sql & " " & sqlTable.Columns(i).ColumnName & ","
Next
sql = Left(sql, sql.Length - 1) & " ) VALUES ( "
For i = 0 To sqlTable.Columns.Count - 1
str = r(i).toString()
dim str2 as string = str.replace("'", "''")
sql = sql & " '" & str2 & "',"
Next
sql = Left(sql, sql.Length - 1) & " );"
'resp.Write(sql & "<br/>")
cmd.CommandText = sql
cmd.ExecuteNonQuery()
Next
conn.Close()
Return True
End Function
Note the name of the the worksheet is the name of the table for the oledb call.
There's a link to other ways of doing this:
http://blogs.msdn.com/b/erikaehrli/archive/2009/01/30/how-to-export-data-to-excel-from-an-asp-net-application-avoid-the-file-format-differ-prompt.aspx
If I have to revisit this problem I'll probably start there.