connect to tableau postgresql in C#

Question

I want to connect to the tableau PostgreSQL server from my .Net framework to list all the reports and datasources published in the tableau server.

For doing this, I have done the following steps.

Added the npgsql.dll reference that i downloaded online
Added the below two namespaces in my class file

using NpgsqlTypes; using Npgsql;
I added the connection sting as follows

I also tried with modifying the connection string with port value and renaming the DataSource to Server, Initial catalog to Database and provider Name to Npgsqll

My Method is as follows:

public DataTable  getAllDataSourceNames()
{
    DataTable dataSourceNames = new DataTable();
    NpgsqlConnection conServer = new NpgsqlConnection(conString);
    conServer.Open();
    string command = @"select * from datasources";
    NpgsqlDataAdapter sqlcmd = new NpgsqlDataAdapter(command,conServer);
    sqlcmd.Fill(dataSourceNames);
    return dataSourceNames;
}`

No error. I can build and run successfully the other links in the website. But cannot cannot establish connection to my postgresql server.

Any idea of how to establish the connection?

I would suggest you check the tableau community, like this post. By default, the database did not open for outside connection. — Prisoner
– Prisoner, Commented Oct 24, 2017 at 7:58
public string conString = System.Configuration.ConfigurationManager.ConnectionStrings["Tableau_Details"].ConnectionString.ToString(); — fishy101
– fishy101, Commented Oct 24, 2017 at 8:45

Isma · Accepted Answer · 2017-10-24 09:15:50Z

Working with Postgres Connection in c#:

private DataSet ds = new DataSet();
private DataTable dt = new DataTable();
public Form1()
{    
    InitializeComponent();    
}
private void llOpenConnAndSelect_LinkClicked(object sender, 
            LinkLabelLinkClickedEventArgs e)
{
    try
    {
        // PostgeSQL-style connection string
        string connstring = String.Format("Server={0};Port={1};" + 
            "User Id={2};Password={3};Database={4};",
            tbHost.Text, tbPort.Text, tbUser.Text, 
            tbPass.Text, tbDataBaseName.Text );
        // Making connection with Npgsql provider
        NpgsqlConnection conn = new NpgsqlConnection(connstring);
        conn.Open();
        // quite complex sql statement
        string sql = "SELECT * FROM simple_table";
        // data adapter making request from our connection
        NpgsqlDataAdapter da = new NpgsqlDataAdapter(sql, conn);
        // i always reset DataSet before i do
        // something with it.... i don't know why :-)
        ds.Reset();
        // filling DataSet with result from NpgsqlDataAdapter
        da.Fill(ds);
        // since it C# DataSet can handle multiple tables, we will select first
        dt = ds.Tables[0];
        // connect grid to DataTable
        dataGridView1.DataSource = dt;
        // since we only showing the result we don't need connection anymore
        conn.Close();
    }
    catch (Exception msg)
    {
        // something went wrong, and you wanna know why
        MessageBox.Show(msg.ToString());
        throw;
    }
}

The following link may help you: Using PostgreSQL in your C# .NET application

This should be a comment or contain a little brief of the link you have posted.
Yes I tried it. Am getting IOException "Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host" Any idea how I can handle it ?
Try to check your Server to DB if Connected or not.. much better to do it on cmd like Ping Command. Also check your DB Username access previlege.

Hambone · Accepted Answer · 2017-11-04 05:21:42Z

Short answer -- no, not sure what's wrong. Your code doesn't raise any alarm bells.

Somewhat related, and it may help: I'm a big fan of the Connection StringBuilder with Npgsql. Here is a brief example:

NpgsqlConnectionStringBuilder sb = new NpgsqlConnectionStringBuilder();
sb.ApplicationName = "Tableau " + Environment.GetEvironmentVariable("USERNAME");
sb.Host = "1.2.3.4";
sb.Port = 5432;
sb.Username = "foo";
sb.Password = "bar";
sb.Database = "postgres";
sb.Pooling = false;
sb.Timeout = 120;

conServer = new NpgsqlConnection(sb.ToString());

It demistifies all of this and makes injecting parameters easy. I highly recommend you add the ApplicationName property so that when you are monitoring sessions, you will know who is who.

I dont have ApplicationName parameter in NpgsqlConnectionStringBuilder class. and when i provide without specifying the application name. am still getting the same IOException @Hambone
The ApplicationName parameter isn't mandatory at all, but it's helpful. But the fact that it's missing hints that maybe you have a really old version of NpgSql. What versions are NpgSql and your PostgreSQL server?

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