In my project I'm trying to write code that will be nice to understand.
I currently split my data access functions in a seperate class.
What I'm trying to achieve however, is to catch the errors back to my form. I am not getting this currently and I was wondering why.
In my form I have the following code:
private void btn_Save_ItemClick(object sender, ItemClickEventArgs e)
{
if (dal.updatePerson(ObjectAfterSaving))
{
MessageBox.Show("Updated!");
}
else
{
MessageBox.Show("error");
};
}
In my dal object (derived from the DataAccess_Person class), I have the following method:
public bool updatePerson(Person p)
{
conn = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["Database"].ConnectionString);
SqlCommand command = new SqlCommand(#"UPDATE Person
SET PersonName = #PersonName
WHERE PersonID = #PersonID", conn);
command.Parameters.Add("#PersonName", SqlDbType.VarChar).Value = p.Name
{
try
{
if (conn.State == ConnectionState.Closed)
{
conn.Open();
}
int a = command.ExecuteNonQuery();
conn.Close();
if (a > 0)
{
return true;
}
else
{
return false;
}
}
catch (SqlException ex)
{
ex.ToString();
return false;
}
}
}
My question is: let's say if my method falls in the catch. Will my front end (form) show it (Sql Exception for example) ? Or will i just get 'error' ? And If I will just get error, how I can improve my code to show the Exception instead of error?
A simple way is to remove the try catch from your DAL and add it to the form. For example:
private void btn_Save_ItemClick(object sender, ItemClickEventArgs e)
{
var result = "Success";
try
{
dal.updatePerson(ObjectAfterSaving);
}
catch (SqlException sqlEx)
{
result = sqlEx.Message;
}
catch (Exception ex)
{
result = ex.Message;
}
MessageBox.Show(result);
}
Just note that there's a lot of ways you can do this. My preference is to not include DAL specific exception types in my UI. Instead I may return a custom result type that has an errorcode and message and let my UI display that or generate a custom message based on the error code.
You‘ll just get „error“ in case of a SqlException. All other exceptions will crash your program if you don‘t have a global exception handler. If you want to show the error message you could introduce an out variable for the error message:
bool successful = MyMethod(out string errorMessage)
if (!successful)
{
MessageBox.Show(errorMessage);
}
public bool MyMethod(out string errorMessage)
{
errorMessage = "";
try
{
// do some stuff
return true;
}
catch(Exception ex)
{
errorMessage = ex.Message;
return false;
}
}
Related
I am catching an exception and processing it.
Somewhere up the call tree, I am doing the same.
Once I process my exception at the child level, I want to also go ahead and invoke the exception handler, wherever it is, somewhere up the call tree.
For that, I thought I would do run the throw again.
But instead of breaking somewhere up the call tree, it is breaking in the place where I am doing the throw and crashing, at this line:
throw new Exception("Cannot Write Header Row to Database " + Msg);
code:
public static void NewHeaderRow(string FILE_REV_NUMBER, DateTime FILE_CREATE_DATE, string EDC_DUNS_NUMBER, int RunId)
{
SqlConnection connection = null;
try
{
connection = new SqlConnection(ConfigurationManager.ConnectionStrings["DbConn"].ToString());
connection.Open();
SqlCommand com;
com = new SqlCommand("dbo.INSERT_PPL_HEADER", connection);
com.CommandType = CommandType.StoredProcedure;
com.Parameters.Add(new SqlParameter("#FILE_REV_NUMBER", FILE_REV_NUMBER));
com.Parameters.Add(new SqlParameter("#FILE_CREATE_DATE", FILE_CREATE_DATE));
com.Parameters.Add(new SqlParameter("#EDC_DUNS_NUMBER", EDC_DUNS_NUMBER));
com.Parameters.Add(new SqlParameter("#RunId", RunId));
if (com.Connection.State == ConnectionState.Closed) com.Connection.Open();
com.ExecuteNonQuery();
}
catch (Exception e)
{
string Msg;
Msg = "Encountered unexpected program issue. Please contact your program administator. Error details...";
Msg = Msg + System.Environment.NewLine;
Msg = Msg + System.Environment.NewLine;
Msg = Msg + e.ToString();
Msg = Msg + System.Environment.NewLine;
Msg = Msg + System.Environment.NewLine;
Msg = Msg + e.Message;
throw new Exception("Cannot Write Header Row to Database " + Msg);
}
finally
{
if (connection == null) { } else connection.Close();
}
}
Try just using the throw keyword, instead of building a new exception.
https://stackoverflow.com/a/2999314/5145250
To add additional information to the exception warp it in another exception object and pass the original exception as argument with new message to keep the original stack trace in inner exception.
throw new Exception("Cannot Write Header Row to Database " + Msg, e);
At some top level you should handle global exceptions to avoid crashing.
The way I was finally able to pin point the problem was to extremely simplify my code so as to be able to see the problem clearly. I just copied my solution to a new location, and gutted out all the non-essential stuff -- stuff I knew was not going to be important for the purposes of troubleshooting.... Very effective way of troubleshooting difficult problems that are hard to trace.... Here is what I ended up with (the simple code).
I was not catching general exception in the code that calls NewHeaderRow.
I was catching System.IO exception.
So, because code had nowhere to go, it crashed....
It is very hard for the eyes to catch this error and also difficult to trace.
private void button1_Click(object sender, EventArgs e)
{
LoadFile();
}
private static int ProcessHeaderRow(string line)
{
int LoadRunNumber = 0;
try
{
//some complex logic was here; error occurs here, so I throw an exception....
throw new Exception("An Error Occurs -- Process Header Row Try block");
}
catch (CustomExceptionNoMessage e)
{
throw new CustomExceptionNoMessage(e.Message);
}
catch (Exception e)
{
//Process the exception, then rethrow, for calling code to also process the exception....
//problem is here...XXXXXXXXXXXXXXXXXX
throw new Exception(e.Message); //crashes
}
return LoadRunNumber;
}
public static bool LoadFile()
{
int RunId = 0;
try
{
RunId = ProcessHeaderRow("10~~happy~007909427AC");
MessageBox.Show("Completed Upload to Cloud...");
}
catch (CustomExceptionNoMessage ce)
{
MessageBox.Show(ce.Message);
}
catch (System.IO.IOException e) //CHANGED THIS LINE, AND I AM UP AND RUNNING (Changed to Exception e)
{
MessageBox.Show(e.Message);
}
return true;
}
public class CustomExceptionNoMessage : Exception
{
public CustomExceptionNoMessage()
{
}
public CustomExceptionNoMessage(string message)
: base(message)
{
}
public CustomExceptionNoMessage(string message, Exception inner)
: base(message, inner)
{
}
}
private void button1_Click(object sender, EventArgs e)
{
LoadFile();
}
I am creating an app which does some SQL server config, which part of a bigger system
There is a config table in the database of the system as follows:
CREATE TABLE Config
(
ConfigItem NVARCHAR(255) PRIMARY KEY NOT NULL,
ConfigValue NVARCHAR(255) NOT NULL
)
INSERT INTO Config
VALUES
('LinkedServerName','MYLINKEDSERVER'),
('DatabaseName','APPLICATIONDATABASE')
My app is a Windows form with two textboxes and a button. The form also has an initially blank label which is used to display error messages to the user.
In the first text box, the value for the linked server name is shown, in the second, the value for the database is shown. Both are shown on form load.
On clicking the submit button, the two values are updated in the database based on what is in the text boxes.
I have the following code to populate the two textboxes with current values at form load:
private void Form1_Load(object sender, EventArgs e)
{
// populate the textboxes
txtLinkedServer.Text = GetConfigValue("LinkedServerName");
txtDatabase.Text = GetConfigValue("DatabaseName");
}
private string GetConfigValue(string ConfigItem)
{
// get the value for the given config item from the database
using (SqlConnection conn = new SqlConnection(connectionString))
{
DataTable dt = new DataTable();
SqlCommand com = new SqlCommand();
com.CommandText = "SELECT ConfigValue FROM Config WHERE ConfigItem = #ConfigItem";
com.Parameters.AddWithValue("ConfigItem", ConfigItem);
com.Connection = conn;
try
{
conn.Open();
dt.Load(com.ExecuteReader());
if (dt.Rows.Count == 0)
{
return "Error retrieving " + ConfigItem + " name from config table";
}
else
{
return dt.Rows[0]["ConfigValue"].ToString();
}
}
catch
{
return "Error in GetConfigValueMethod when retrieving " + ConfigItem;
}
finally
{
conn.Close();
}
}
}
If there is a problem with retrieving the config data (caught by the catch block in GetConfigValue) I want the label to show the string returned from GetConfigValue.
What is the best / neatest way to do this? I was thinking
private void Form1_Load(object sender, EventArgs e)
{
string message;
// populate the textboxes
try
{
message = GetConfigValue("LinkedServerName");
txtLinkedServer.Text = message
}
catch
{
lblFeedback.Text = message;
}
// do the same for the database here
}
however, I cannot do that as I get
Use of unassigned local variable 'Message'
Or am i best to change the GetConfigValue method so that it throws it's own exception in the catch block rather than returning a string and catching that in the Load method as follows;
private string GetConfigValue(string ConfigItem)
{
// get the value for the given config item from the database
using (SqlConnection conn = new SqlConnection(connectionString))
{
// same code here
try
{
// same code here
}
catch
{
Throw new Exception ("Error in GetConfigValueMethod when retrieving " + ConfigItem);
}
finally
{
conn.Close();
}
}
}
private void Form1_Load(object sender, EventArgs e)
{
// populate the textboxes
try
{
txtLinkedServer.Text = GetConfigValue("LinkedServerName");
}
catch (Exception e)
{
lblFeedback.Text = e.Message;
}
// do the same for the database here
}
Or some other way completely?
Looking at your second example, if that's the result you want, then it looks like you just need to replace
catch
{
lblFeedback.Text = message;
}
in your first example with
catch (Exception e)
{
lblFeedback.Text = e.Message;
}
from your second example.
As error message says you tried to use unassigned variable 'message' and because of that you were getting that error.
Try this:
private void Form1_Load(object sender, EventArgs e)
{
string message = String.Empty;
// populate the textboxes
try
{
message = GetConfigValue("LinkedServerName");
txtLinkedServer.Text = message
}
catch (Exception ex)
{
if (!String.IsNullOrEmpty(message))
lblFeedback.Text = message;
else
lblFeedback.Text = ex.Message;
}
// do the same for the database here
}
I want to show a message box on client side When a call is returned from service.
It is confirmed service runs and saves data into Database but call does not return.
I Google it but did not find a way
Here is my client code
private void button1_Click(object sender, EventArgs e)
{
try {
string ide = txt_id.Text;
int id = int.Parse(ide);
string city = txt_city.Text;
Service1Client client = new Service1Client();
if (client.insert(id, city))
{
client.Close();
MessageBox.Show("Your changes were saved");
}
}
catch(Exception ex)
{
Console.WriteLine(ex);
}
}
Service code
public bool insert(int id,string city)
{
Ship s = new Ship
{
order_id = id,
shipcity = city,
order_date = DateTime.Now
};
ShipsDataContext od = new ShipsDataContext();
od.Ships.InsertOnSubmit(s);
try
{
od.SubmitChanges();
Console.ReadKey();
return true;
}
catch (Exception ex)
{
Console.WriteLine(ex);
return false;
}
}
You are waiting for console input:
Console.ReadKey();
Btw, that error handling is a problem because you are suppressing bugs (by discarding all error information) and in case of error you do nothing.
I have a subroutine. It comapares whether values are empty then doing something. For example, if they are empty, then warnings are raised.
The code works fine. But when value are not empty, the warnings are still pop out. Please help me to correct the logic.
Thanks.
private void btnNew_Click(object sender, EventArgs e)
{
try
{
if (txtbox1.Text.ToString().Trim() == string.Empty)
{
goto Msg1;
}
if (txtbox2.Text.ToString().Trim() == string.Empty)
{
goto Msg2;
}
DataRow dr = mydataSet.Tables[0].NewRow();
dr["Descript"] = txtbox1.Text;
dr["Abbr"] = txtbox2.Text;
dr["SortOrder"] = Convert.ToDecimal(numericOrder.Value);
if (SortOrders.Contains((decimal)dr["SortOrder"]))
{
goto Msg3;
}
mydataSet.Tables[0].Rows.Add(dr);
dgv.DataSource = mydataSet.Tables[0];
Msg1:
MessageBox.Show("Description is required.");
Msg2:
MessageBox.Show("Abbr is required.");
Msg3:
MessageBox.Show("Please select another one, this one is already used.");
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
}
From the above code, you see. if txtbox1 has some value, the program still displays Msg1. I want to avoid it.
Because labels are just labels, and code after them is executed sequentially.
Why can't you do just this:
try
{
if (txtbox1.Text.ToString().Trim() == string.Empty)
{
MessageBox.Show("Description is required.");
return;
}
if (txtbox2.Text.ToString().Trim() == string.Empty)
{
MessageBox.Show("Abbr is required.");
return;
}
DataRow dr = mydataSet.Tables[0].NewRow();
dr["Descript"] = txtbox1.Text;
dr["Abbr"] = txtbox2.Text;
dr["SortOrder"] = Convert.ToDecimal(numericOrder.Value);
if (SortOrders.Contains((decimal)dr["SortOrder"]))
{
MessageBox.Show("Please select another one, this one is already used.");
return;
}
mydataSet.Tables[0].Rows.Add(dr);
dgv.DataSource = mydataSet.Tables[0];
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
It's so much more readable.
Restructure your code to avoid goto - it is a relic and not much use in a properly object oriented codebase.
Returning from the method, throwing exceptions or building an errors dictionary are all better options than using goto.
For example, you can have a List<string> errors which you add to when you get an error condition.
If it is empty, no errors were encountered, if it isn't, there were.
This is a good case were goto is the wrong way to go. Use something like this instead.
private void btnNew_Click(object sender, EventArgs e)
{
try
{
bool error = false;
if (txtbox1.Text.ToString().Trim() == string.Empty)
{
MessageBox.Show("Description is required.");
error = true;
}
if (txtbox2.Text.ToString().Trim() == string.Empty)
{
MessageBox.Show("Abbr is required.");
error = true;
}
if (SortOrders.Contains(Convert.ToDecimal(numericOrder.Value)
{
MessageBox.Show("Please select another one, this one is already used.");
error = true;
}
if(error)
return;
DataRow dr = mydataSet.Tables[0].NewRow();
dr["Descript"] = txtbox1.Text;
dr["Abbr"] = txtbox2.Text;
dr["SortOrder"] = Convert.ToDecimal(numericOrder.Value);
mydataSet.Tables[0].Rows.Add(dr);
dgv.DataSource = mydataSet.Tables[0];
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
}
Edit
Just figured that my code didn't actually do the same as his first sample since it only displayed the first error no matter how many that occured. Updated my sample to accomodate for that.
I've always been taught to avoid goto like the plague, and it's something I've followed for years. I've never even considered it to be an option when writing code.
Thinking about it though, I did read an article a few years ago (which I can't find now) which said you could credibly use gotos only if you used it to jump down code, and not up: a rule that is stuck to here.
Check here for more info: Does anyone still use [goto] in C# and if so why?
There are better ways of using goto statement, for instacne using "return" (when used in the middle of a method), "break" and "continue". Have you ever used one of these?
private void btnNew_Click(object sender, EventArgs e)
{
try
{
var description = txtbox1.Text.Trim();
if (string.IsNullOrEmpty(description))
{
MessageBox.Show("Description is required.");
return;
}
var abbr = txtbox2.Text.Trim();
if (string.IsNullOrEmpty(abbr))
{
MessageBox.Show("Abbr is required.");
return;
}
var numericOrderValue = Convert.ToDecimal(numericOrder.Value);
if (SortOrders.Contains(numericOrderValue)
{
MessageBox.Show("Please select another one, this one is already used.");
return;
}
DataRow dr = mydataSet.Tables[0].NewRow();
dr["Descript"] = description;
dr["Abbr"] = abbr;
dr["SortOrder"] = numericOrderValue;
mydataSet.Tables[0].Rows.Add(dr);
dgv.DataSource = mydataSet.Tables[0];
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
}
private void btnNew_Click(object sender, EventArgs e)
{
try
{
if (txtbox1.Text.ToString().Trim() == string.Empty)
{
MessageBox.Show("Description is required.");
}
if (txtbox2.Text.ToString().Trim() == string.Empty)
{
MessageBox.Show("Abbr is required.");
}
DataRow dr = mydataSet.Tables[0].NewRow();
dr["Descript"] = txtbox1.Text;
dr["Abbr"] = txtbox2.Text;
dr["SortOrder"] = Convert.ToDecimal(numericOrder.Value);
if (SortOrders.Contains((decimal)dr["SortOrder"]))
{
MessageBox.Show("Please select another one, this one is already used.");
}
mydataSet.Tables[0].Rows.Add(dr);
dgv.DataSource = mydataSet.Tables[0];
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
}
Try this. It works.
My code looks like this:
public bool myQuery(string cmd)
{
try
{
OracleCommand command = null;
command = new OracleCommand(cmd, sqlConnection);
command.ExecuteReader();
}
catch (Exception ex)
{
MessageBox.Show(ex.Message, "error!");
return false;
}
return true;
}
My issue is when error ORA-02291 occurs in Oracle, its Exception is not caught. No error is shown, how do I catch this error ?
Check this:
if (ex.InnerException != null)
{
MessageBox.Show(ex.InnerException.Message, "error!");
}
catch (System.Data.OracleClient.OracleException ex)
{
int code = ex.Code;
// or
string eCode = ex.ErrroCode;
return false;
}
return true;