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To export Postgres DB to excel using c#

I need to export Postgres DB (having around 20 tables) to excel using C#. I need to implement some logic on the data from DB and then need to export it. Any idea of how to export all data using c#?

using Npgsql;
using OfficeOpenXml; // Nuget EPPlus
using System.IO;
EPPlus has a one-step method to export a data table into a spreadsheet, so if you leveraged this, you should be able to loop through your queries and export each one to a unique sheet.
Something like this (untested but should be 99% there) should do the trick:
FileInfo fi = new FileInfo("foo.xlsx");
ExcelPackage excel = new ExcelPackage(fi);
int sheet = 1;
foreach (string sql in sqlQueries)
{
DataTable dt = new DataTable();
NpgsqlCommand cmd = new NpgsqlCommand(sql, conn);
NpgsqlDataAdapter da = new NpgsqlDataAdapter(cmd);
da.Fill(dt);
ExcelWorksheet ws = excel.Workbook.Worksheets.Add(string.Format("Sheet{0}", sheet++));
ws.Cells["A1"].LoadFromDataTable(dt, true);
}
excel.Save();
Of course, I'd recommend some refinements to deal with datatypes, formatting and the like, but this is the basic construct.
Also, of course, use the IDisposable using liberally.

The problem can be divided into two sub problems
Getting Data into c# from postgres.
pushing that data into excel.
Now solving a problem at a time
Here is a good article on working with postgres using c#
once you have you data in c# you can use any one of many libraries available for working with Excel using c#
One of them is NPOI
Here is one with example
Happy Coding.!!!

How to save an Excel file via ssms or c# in a SQL Server 2016 database? [closed]

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I'm trying to save an existing Excel file via ssms OR C# into my SQL Server 2016 database.
I want to save each row of my Excel file in a C# object and then save it into my database, or do you have better ideas?
I also thought about saving the Excel file as a *.csv and import this file via ssms in my database.
Which of these two ideas would you recommend or is there any other way to solve this problem?
If you have any questions, I would be pleased to answer them.
I thank you in advance for all the answers and tips!

For your problem you can try below approaches:
1) Using SQLBulkcopy:
SqlBulkCopy class as the name suggests does the bulk insert from one source to another and hence all rows from the Excel sheet can be easily read and inserted using the SqlBulkCopy class.
protected void Upload(object sender, EventArgs e)
{
//Upload and save the file
string excelPath = Server.MapPath("~/Files/") + Path.GetFileName(FileUpload1.PostedFile.FileName);
FileUpload1.SaveAs(excelPath);
string conString = string.Empty;
string extension = Path.GetExtension(FileUpload1.PostedFile.FileName);
switch (extension)
{
case ".xls": //Excel 97-03
conString = ConfigurationManager.ConnectionStrings["Excel03ConString"].ConnectionString;
break;
case ".xlsx": //Excel 07 or higher
conString = ConfigurationManager.ConnectionStrings["Excel07+ConString"].ConnectionString;
break;
}
conString = string.Format(conString, excelPath);
using (OleDbConnection excel_con = new OleDbConnection(conString))
{
excel_con.Open();
string sheet1 = excel_con.GetOleDbSchemaTable(OleDbSchemaGuid.Tables, null).Rows[0]["TABLE_NAME"].ToString();
DataTable dtExcelData = new DataTable();
//[OPTIONAL]: It is recommended as otherwise the data will be considered as String by default.
dtExcelData.Columns.AddRange(new DataColumn[3] { new DataColumn("Id", typeof(int)),
new DataColumn("Name", typeof(string)),
new DataColumn("Salary",typeof(decimal)) });
using (OleDbDataAdapter oda = new OleDbDataAdapter("SELECT * FROM [" + sheet1 + "]", excel_con))
{
oda.Fill(dtExcelData);
}
excel_con.Close();
string consString = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
using (SqlConnection con = new SqlConnection(consString))
{
using (SqlBulkCopy sqlBulkCopy = new SqlBulkCopy(con))
{
//Set the database table name
sqlBulkCopy.DestinationTableName = "dbo.tblPersons";
//[OPTIONAL]: Map the Excel columns with that of the database table
sqlBulkCopy.ColumnMappings.Add("Id", "PersonId");
sqlBulkCopy.ColumnMappings.Add("Name", "Name");
sqlBulkCopy.ColumnMappings.Add("Salary", "Salary");
con.Open();
sqlBulkCopy.WriteToServer(dtExcelData);
con.Close();
}
}
}
}
Here this code adds an excel sheet with three columns as Id, Name and Salary.
2) Using DTS in SSMS:
You can use the SQL Server Data Transformation Services (DTS) Import Wizard or the SQL Server Import and Export Wizard to import Excel data into SQL Server tables. When you are stepping through the wizard and selecting the Excel source tables, remember that Excel object names that are appended with a dollar sign ($) represent worksheets (for example, Sheet1$), and that plain object names without the dollar sign represent Excel named ranges.
3) Using SSIS package:
You can create SSIS package to import excel file. For this, you can use BIDS in Visual Studio or SQL Server Data tools.
You can give your excel file as excel source and in the target give your SQL server database table.
Perform the necessary mappings and you're good to go.
Now, you must be having a question like When to use which approach?
Use approach 1, Whenever you're providing functionality to import excel file at the user end, i.e. according to application requirement, the user can upload local excel sheet. For this use case, one thing you should look out is, the user must be aware of the template. If you have written code to import excel with 3 columns and the user tries to import with 4 columns, you will have some error in future. So make sure that you provide a template that user should download and fill and upload it.
Use approach 2, whenever you want to load data for only one time, or you can say that you want to perform initial load. You can use this approach as it's most simple and requires less time to do the configuration.
Use approach 3, whenever you have some requirement like to import excel data on the timely basis from some shared location. For ex, you are importing monthly mobile bills to your database provided by some vendor. You can create a package for this functionality and do the SSIS configuration and create a package.
Once the package is created you can create a SQL job and schedule it as per the requirements.

You can use BulkInsert to imports a data file into a database table or view in a user-specified format in SQL Server

As all, it depends on usage, change frequency, who is going to maintain solution etc.
SSIS and CSV import
It is possible to create SSIS package which would be able to import your data automatically when deployed on MSSQL server or manually. This would be simplest/quickest to implement. One of advantages when using Visual Studio tooling for SSIS development you would have visual representation of mappings, flow.
Drawback, even though I have seen automated column mapping updates (C# automatic SSIS package generation), whenever you would need to add, remove, change column, you would need a manual change.
BCP
MS console utility which you can use to define columns in format files and import your CSVs. Drawback is that you there is no graphical user interface, though many would argue that this is an advantage because there is a better overview for changes.
ORM
In object relational mapping solution you would need to translate your Excel file into object oriented programming language classes and save as objects into database table. Drawback is that you need to have some programming knowledge, but would pay off in a longer run because potentially your solution could get the data directly form source for those excel sheets.

Export to excel without using the com object

I'm exporting a dataset to an Excel sheet, but I don't want to use the COM of Excel, because it takes a lot of time.
I need a method that exports to Excel without using the MS Office Interop, and I need to load the method using an empty Excel template so that the new Excel sheet has the same format.

You could reach an excel file and update its contents using ADO.NET and the Jet OleDbProvider
string con = #"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=your_path\test.xls;Extended Properties='Excel 8.0;HDR=No;'";
using(OleDbConnection c = new OleDbConnection(con))
{
c.Open();
string commandString = "Insert into [Sheet1$] (F1, F2, F3) values('F1Text', 'F2Text', 'F3Text')" ;
using(OleDbCommand cmd = new OleDbCommand(commandString))
{
cmd.Connection = c;
cmd.ExecuteNonQuery();
}
}

I use EPPlus. Available via Nuget and LGPL licensed. Let's you create and manage xlsx spreadsheets using OOXML.

I would look into something like this xlslinq
But you can also use this library as it will export it to a dataset

I would suggest using the Open XML SDK 2.0
You will be able to do everything you requested and on top of that it is very fast.

Import Excel to database in C#.NET

I have a huge collection of Excel files. there are many information privite and my client want to store it in database. And later they can use the data in the database to rebuild all the Excel report. So do you have any idea to achieve that? what if I convert Excel to byte stream to store?
I know that if i put Excel to byte stream, will use more time and space to handle like formats and other thing, and stupid to do that. So I would like other way to store the data?

As Uriel_SVK said, Interop.Excel should be easy to achieve that. But if you just wish to store datas, can also have a try with Oledb.
string myConnection ="Provider=Microsoft.ACE.OLEDB.12.0;Data Source=D:\test.xlsx;Extended Properties="Excel 12.0 ;HDR=YES";
OleDbConnection conn = new OleDbConnection(connstr);
string strSQL = "SELECT * FROM [Sheet$]";
OleDbCommand cmd = new OleDbCommand(strSQL, conn);
DataSet dataset = new DataSet();
OleDbDataAdapter adapter = new OleDbDataAdapter(cmd);
adapter.Fill(dataset);
GridViewXYZ.DataSource = dataset;
GridViewXYZ.DataBind();

Are you constrained to using C#? Certain versions of SQL Server offer DTS or SSIS services for moving data in and out of the database from various sources/destinations such as Excel files. Oracle has something similar in OWB.

You can use Jet OleDB.
The sheet will be the tables and the workbook will be the database. You can use SQl query to produce the data what you want and save it on a datatable/dataset

Loading excel column data using C# in a dropdown menu

I want to load a column in excel into a selectable dropdown menu using c#. I have access to the file, and can load the file in C#, but am not sure how to implement what I want. Suggestions? (I'm using Visual Studio 2008)

You can use the OleDb Managed Data Provider to read an Excel spreadsheet using ADO.NET just like you would with a database.
using System.Data.OleDb;
DataTable dt = new DataTable();
string connString = #"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=c:\Book1.xls;Extended Properties='Excel 8.0;HDR=NO'";
using (OleDbConnection conn = new OleDbConnection(connString))
{
conn.Open();
//Where [F1] = column one, [F2] = column two etc, etc.
OleDbCommand selectCommand = new OleDbCommand("select [F1] AS [id] from [Sheet1$]",conn);
OleDbDataAdapter adapter = new OleDbDataAdapter();
adapter.SelectCommand = selectCommand;
adapter.Fill(dt);
}
listBox1.DataSource = dt;
listBox1.DisplayMember = "id";

You could implement a PIA solution something like this (assuming 5 items in column "A" of the first worksheet):
using Excel = Microsoft.Office.Interop.Excel;
...
worksheet = workbook.Worksheets[1] as Excel.Worksheet;
Excel.Range range;
range = worksheet.get_Range("A1", "A5") as Excel.Range;
foreach (Excel.Range cell in range.Cells)
{
myComboBox.Items.Add(cell.Value2 as string);
}
If you don't know the exact number if items in the dropdown at runtime, you will need to search the range to find the end; check out this sample here.
This sample uses the Office 2007 PIAs, if you are using an older version the syntax should be very close but might vary a bit.

As far as I know you only have a couple of options:
Primary Interop Assemblies (PIA) that let you read and write from the Excel object model.
Building a Visual Studio Tools for Office (VSTO) solution, which effectively lets you write 'code behind' for your Excel spreadsheet. Depending on what you are trying to achieve this can make sense if you are actually doing a lot of work within excel, and your current application is really just creating an extension to the spreadsheet UI.