PostgreSQL Error 28P01密码认证失败求助：VS2017项目连接异常

Hey there, let's work through this Error 28P01 issue together—since your postgres account works perfectly in DataGrip, the problem is almost certainly related to how your WinForms project is handling connection details or authentication rules. Here are the key checks to run:

• Double-check your connection string for typos or mismatches
  First, locate your connection string in the App.config file of your project. Make sure the User Id and Password values match exactly what you use in DataGrip—no extra spaces, missing characters, or unescaped special symbols (like @, &, or # in your password, which might need to be wrapped in quotes). A standard valid string looks like this:

  Server=localhost;Port=5432;Database=YourDatabaseName;User Id=postgres;Password=YourExactPassword;
  

  Note: Depending on the PostgreSQL driver you're using (e.g., Npgsql vs. ODBC), the key names might vary—some use Username instead of User Id, so confirm your driver's required syntax.

• Verify the connection string your app is actually using at runtime
  It's possible that the connection string you tested in VS's data source wizard isn't the one your app uses when running. To confirm, add a quick debug check right before you try to populate the ListBox:

  MessageBox.Show(yourSqlConnection.ConnectionString);
  

  Compare the output to the connection details you use in DataGrip—this will catch cases where a different config file (like App.Debug.config) is overriding your settings, or if you hardcoded a different string in code.

• Check PostgreSQL's pg_hba.conf authentication rules
  Even though DataGrip connects fine, your WinForms app might be hitting a different authentication rule in PostgreSQL's host-based access config. Here's how to check:

  1. Find pg_hba.conf in your PostgreSQL installation's data folder (e.g., C:\Program Files\PostgreSQL\15\data).
  2. Look for entries for local/localhost connections. Ensure they use md5 authentication (the same method DataGrip uses) instead of peer or ident, which can fail for Windows apps. Example valid entries:

     host    all             all             127.0.0.1/32            md5
     host    all             all             ::1/128                 md5
     

  3. Save the file and restart the PostgreSQL service for changes to take effect.

• Confirm driver compatibility and update if needed
  Outdated PostgreSQL drivers for .NET can cause authentication mismatches, especially if your PostgreSQL server is a newer version. In VS 2017, open the NuGet Package Manager for your project, search for Npgsql (the most common .NET driver for PostgreSQL), and update it to the latest version compatible with your .NET Framework and PostgreSQL server.

• Rule out cached or overwritten configs
  Sometimes VS caches old connection settings, or your output directory's .exe.config file doesn't reflect your latest changes. To fix this:

  1. Clean your project (Build → Clean Solution) then rebuild it.
  2. Navigate to your project's bin/Debug folder, open the .exe.config file, and verify the connection string inside matches what you expect.

内容的提问来源于stack exchange，提问作者Jejh