'An unhandled exception of type 'MySql.Data.MySqlClient.MySqlException' occurred in MySql.Data.dll
Additional information: Unable to connect to any of the specified MySQL hosts.'
Even though I have no errors according to C#. My program will keep displaying this error message when I try to run the program. Can some help?
As is stated in a comment: The error is that the connection to the MySQL host cannot be created (could be wrong password, wrong username, wrong serverip, wrong port being used, .... or that the mysql server is not running at all, ... thus these are the things you should check first).
Another thing is that you sounded confused that the compilation did not show any errors. You can think of it this way: When you compile the syntax and the grammatics are checked if they are ok and appropriate errors shown. BUT what values are there during a run is NOT checked. That is what is done during a run and causes the error you asked about.
Thus compilation does only check if the syntax is correct not if you really manage to connect to soemthing or if the values you are storing in the variables are the ones you expect there to be.
Related
I've been trying to follow several different tutorials with EFCore and .net core and I've been totally blocked at the point where I try and create a local database.
I've used both the powershell tools and the commandline tools to try and create an initial migration (or do anything, really).
I consistently get the error:
System.InvalidOperationException: An exception has been raised that is likely due to a transient failure. Consider enabling transient error resiliency by adding 'EnableRetryOnFailure()' to the 'UseSqlServer' call.
---> Microsoft.Data.SqlClient.SqlException (0x80131904): A connection was successfully established with the server, but then an error occurred during the login process. (provider: Named Pipes Provider, error: 0 - No process is on the other end of the pipe.)
The database does not currently exist on the system, though local SQL Server appears to be up and running.
Here is the c# code for adding the context:
services.AddDbContextPool<TestDbContext>(options =>
options.UseSqlServer(Configuration.GetConnectionString("TestDb")
)
);
This is the connection string code:
"TestDb": "Data Source=(localdb)\\MSSQLLocalDB;Initial Catalog=TestDb"
I get similar errors whether I run add-migration, dotnet ef migration add, or dotnet ef dbcontext info. (note: with the dotnet calls I am using the -s ..\{webproject}\{webproject}.csproj property
I've also messed with the connection string by adding various combinations of Trusted_Connection=True; MultipleActiveResultSets=True;, and Integrated Security=true.
I've gone into SSMS and ensured the Server authentication is SQL Server and Windows Authentication Mode and that Maximum Connections is set to 0 (unlimited). I've also gone to logins and tried adding the user to pretty much all the server roles.
So, yeah, I'm pretty confused. I've worked with EF for years, though this is my first experience with EFCore and I'm definitely more of a developer than a SQL Admin. This is also my first time trying to use the local db on this particular computer.
Edit: Looking at error.log in AppData\Local\Microsoft\Microsoft SQL Server Local DB\Instances\mssqllocaldb I see this error:
2020-01-28 10:15:03.50 Logon Error: 18456, Severity: 14, State: 38.
2020-01-28 10:15:03.50 Logon Login failed for user 'LAPTOP-NC6HQ4TB\ripli'. Reason: Failed to open the explicitly specified database 'TestDb'. [CLIENT: <named pipe>]
Which is confusing. Of course I can't open the specified database. The entire point is I want to create a DB that doesn't yet exist.
Found the answer. Sorry to everyone who tried to help, as you wouldn't have had enough information to solve it.
In the DbContext I had tried to add some code to the constructor to try and populate some data to the database as part of a test. This caused several problems. If the Database hadn't yet been created it tried to connect to the DB before it had been created, which caused the problems I described.
Furthermore, if I had created the db manually it would try to access the DbSets (which had not yet been created), and then complain that the set name was invalid (which, at this point it was.
This all might have been fine if the DB had been created in advance, but since I was using the DbContext to construct the database, it understandably caused problems.
And all of this headache would have been avoided had I not violated SRP and not tried to (even temporarily) hijack a context constructor to hack in some test data.
The takeaway here? Don't pollute your constructors with unrelated hacks. Bleh.
My report is working all the while, until it suddenly hitting this error "An error occurred during local report processing." . I am not able to locate the actual problem.
_reportViewer.LocalReport.SetParameters(rptParameter); //<--Hit error
I have try the solution on An error occurred during local report processing..The definition of the report '' is invalid , but it is still not working
Please advice .
This is the most generic error you can find working with rdlc.
You have to catch the Exception and give a look at the various levels of InnerException; i.e.:
ex.Message
ex.InnerException.Message
ex.InnerException.InnerException.Message
Maybe try to allow null the parameter you have,
i think you are sending a nothing value on that parameter and your parameter is not design to accept null value, so error will occur.
if the problem still there, try to add screen shot
What's wrong with this? I get the exception
An unhandled exception of type 'System.Net.WebException' occurred in System.dll
Additional information: An exception occurred during a WebClient request."
Here's the part of the code with the WebClient.
I need to learn how to use the code part properly one day....
http://pastebin.com/1Z90bvqB
Any answers are greatly appreciated.
(I'm not sure I agree with the ethics of the code itself, but ignoring that...) a WebException is caused by a line that connects to the internet, so either one of the lines like:
webClient.DownloadFile(String.Copy(WeepCraft), #"%appdata%\.minecraft\versions");
Or the line:
Process.Start("http://www.wirez.cf/");
In the latter case, unless I'm misunderstanding, is this actually a process you can start??
Anyway, around all the lines, you'll need to have a try/catch for WebException in case it can't connect for whatever reason (eg Internet down, wrong URL used, server returns HTTP Error code etc etc), and decide how to handle it.
It's a pretty common Exception whenever something tries to do a http request and the server can't be connected to for whatever reason.
This is the second time I got following error for my website:
Warning: Fatal error 9001 occurred at May 5 2012 1:16AM. Note the
error and time, and contact your system administrator.
I get this error while login to website. However, there is no any problem for connecting database or fetching records.
Last time I just took a backup and restore my database then this issue was resolved. But, I got again similar issue, now I want to know exact cause for this error.
I appreciate your reply.
Check SQL Server logs, seems to be an issue with log being full. "Last time I just took a backup and restore my database then this issue was resolved." seems to be database related. Check https://serverfault.com/questions/238394/diagnosing-microsoft-sql-server-error-9001-the-log-for-the-database-is-not-avai.
Here is the complete error message:
An exception of type
'System.Web.HttpException' occurred in
System.Web.dll but was not handled in
user code
Additional information: The remote
host closed the connection. The error
code is 0x80070057.
and the offending code:
char[] buffer = oPage.HTML.HTML.ToCharArray();
Page.Response.Write(buffer, 0, buffer.Length);
Page.Response.Flush();
Page.Response.End();
The oPage.HTML.HTML is a string in a custom page object used by our app. The exception triggers on Page.Flush() and appears to be benign -- I just hit "continue" and everything goes along fine. This never appears at run time.
I have chased many, many Google hits down many rabbit holes and have found nothing. Visual Studio 2005, Vista Ultimate (IIS7).
I've been dealing with this same error for a while now, and my understanding is that when Flush is called, there must be a connection on the other end, otherwise, this error is thrown. It's easy to get into a "fire-and-forget" kind of model when writing web pages, but when the client disconnects (in this debugging case, you're the client), there's nowhere to flush to.
There are two solutions I've found to this:
Wrap Response.Flush and catch the exception.
Check Response.IsClientConnected before you call flush.
I'm not 100% sure about the second one...I'm still in the process of checking that one out.
Good luck!