# How to connect .Net app to Postges

**URL:** <https://community.fly.io/t/how-to-connect-net-app-to-postges/14726>\
**Category:** Questions / Help\
**Tags:** postgres, dotnet, login-only\
**Created:** [August 10, 2023, 6:25am UTC](https://community.fly.io/t/how-to-connect-net-app-to-postges/14726 "2023-08-10T06:25:07Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![CunningLobster](https://sea1.discourse-cdn.com/fly1/user_avatar/community.fly.io/cunninglobster/32/14418_2.png) [@CunningLobster](https://community.fly.io/u/CunningLobster)\
**Post date:** [August 10, 2023, 6:25am UTC](https://community.fly.io/t/how-to-connect-net-app-to-postges/14726/1 "2023-08-10T06:25:08Z")

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Hi!  
I don’t understand how to connect to postgres cluster.

I deployed a .Net app. Then created pg cluster. After that I attached my app to postgres by using this command:  
`flyctl postgres attach --app <app-name> <postgres-app-name>`  
And got the connection string, stored in app secrets:  
`DATABASE_URL=postgres://app-name:password@hostname:5432/app-name?sslmode=disable`  
But when I run the deployed app I receive such an error at the webpage:

# Error.

## An error occurred while processing your request.

**Request ID:** `00-dbc3f379efb8c9743f8bc8dcd3977e82-3c0bb27ffcc72636-00`

### Development Mode

Swapping to **Development** environment will display more detailed information about the error that occurred.

**The Development environment shouldn’t be enabled for deployed applications.** It can result in displaying sensitive information from exceptions to end users. For local debugging, enable the **Development** environment by setting the **ASPNETCORE\_ENVIRONMENT** environment variable to **Development** and restarting the app.

In logs I got this:  
`System.ArgumentException: Couldn't set postgres:<my connection string> (Parameter '<my connection string>')`

What am I doing wrong?

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<div class="post-metadata">

**Author:** ![CunningLobster](https://sea1.discourse-cdn.com/fly1/user_avatar/community.fly.io/cunninglobster/32/14418_2.png) [@CunningLobster](https://community.fly.io/u/CunningLobster)\
**Post date:** [August 11, 2023, 5:50am UTC](https://community.fly.io/t/how-to-connect-net-app-to-postges/14726/2 "2023-08-11T05:50:38Z")

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Ok, I’ve found the solution…  
The problem is the default connection string, provided by [fly.io](http://fly.io), doesn’t work for [asp.net](http://asp.net) application. To solve this problem it’s required to parse this string:

```auto
//Connection to the database
string connectionString = String.Empty;
if (builder.Environment.IsDevelopment())
    connectionString = builder.Configuration.GetConnectionString("DefaultConnection");
else
{
    // Use connection string provided at runtime by Fly.
    var connUrl = Environment.GetEnvironmentVariable("DATABASE_URL");
    
    // Parse connection URL to connection string for Npgsql
    connUrl = connUrl.Replace("postgres://", string.Empty);
    var pgUserPass = connUrl.Split("@")[0];
    var pgHostPortDb = connUrl.Split("@")[1];
    var pgHostPort = pgHostPortDb.Split("/")[0];
    var pgDb = pgHostPortDb.Split("/")[1];
    var pgUser = pgUserPass.Split(":")[0];
    var pgPass = pgUserPass.Split(":")[1];
    var pgHost = pgHostPort.Split(":")[0];
    var pgPort = pgHostPort.Split(":")[1];
    var updatedHost = pgHost.Replace("flycast", "internal");

    connectionString = $"Server={updatedHost};Port={pgPort};User Id={pgUser};Password={pgPass};Database={pgDb};";
};

```

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**Author:** ![catflydotio](https://sea1.discourse-cdn.com/fly1/user_avatar/community.fly.io/catflydotio/32/14559_2.png) [@catflydotio](https://community.fly.io/u/catflydotio)\
**Post date:** [April 27, 2024, 12:54am UTC](https://community.fly.io/t/how-to-connect-net-app-to-postges/14726/3 "2024-04-27T00:54:28Z")

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From #How To to #Questions / Help

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<div class="post-metadata">

**Author:** ![catflydotio](https://sea1.discourse-cdn.com/fly1/user_avatar/community.fly.io/catflydotio/32/14559_2.png) [@catflydotio](https://community.fly.io/u/catflydotio)\
**Post date:** [April 27, 2024, 12:54am UTC](https://community.fly.io/t/how-to-connect-net-app-to-postges/14726/4 "2024-04-27T00:54:28Z")

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Added #dotnet

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**Author:** ![system](https://global.discourse-cdn.com/fly1/original/3X/6/e/6e8955d00cb218e186ebbe3a6ab06fefdce15290.svg) [@system](https://community.fly.io/u/system)\
**Post date:** [May 4, 2024, 12:54am UTC](https://community.fly.io/t/how-to-connect-net-app-to-postges/14726/5 "2024-05-04T00:54:40Z")

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