CredUIPromptForCredentials

[DllImport("Credui.dll", SetLastError = true)]
public static extern CREDUI_RETURN CredUIPromptForCredentials(
   ref CREDUI_INFO pUiInfo,
   [MarshalAs(UnmanagedType.LPStr)] string pszTargetName,
   IntPtr Reserved,
   uint dwAuthError,
   StringBuilder pszUserName,
   uint ulUserNameMaxChars,
   StringBuilder pszPassword,
   uint ulPasswordMaxChars,
   [MarshalAs(UnmanagedType.Bool)] ref bool pfSave,
   CREDUI_FLAGS dwFlags
);

Microsoft documentation: Link