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Writing to App.Config File in C#
Posted on 2016-07-21
All,
I am trying to create a application via C# that writes a value to the AppConfig file. But I am often prompted with this error message when I run the program the first time. However, when I run it after the first run, it'll execute fine. Can someone explain what is happening? I try to set the debugger , but I assume it's probably a timing issue.
I tried this by executing the .exe file in the bin folder of the program so there's no issues writing to the config file.
Error:
Object reference not set to an instance of an object.
App.config
-------------
Program.cs
----------
MethodHelper.cs
----------
I am trying to create a application via C# that writes a value to the AppConfig file. But I am often prompted with this error message when I run the program the first time. However, when I run it after the first run, it'll execute fine. Can someone explain what is happening? I try to set the debugger , but I assume it's probably a timing issue.
I tried this by executing the .exe file in the bin folder of the program so there's no issues writing to the config file.
Error:
Object reference not set to an instance of an object.
App.config
-------------
<?xml version="1.0"?>
<configuration>
<startup>
<supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5.2"/>
</startup>
<appSettings>
<add key="OrderNumber"/>
</appSettings>
<system.web>
<membership defaultProvider="ClientAuthenticationMembershipProvider">
<providers>
<add name="ClientAuthenticationMembershipProvider" type="System.Web.ClientServices.Providers.ClientFormsAuthenticationMembershipProvider, System.Web.Extensions, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" serviceUri=""/>
</providers>
</membership>
<roleManager defaultProvider="ClientRoleProvider" enabled="true">
<providers>
<add name="ClientRoleProvider" type="System.Web.ClientServices.Providers.ClientRoleProvider, System.Web.Extensions, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" serviceUri="" cacheTimeout="86400"/>
</providers>
</roleManager>
</system.web>
</configuration>
Program.cs
----------
public class PurchaseOrder850
{
static public void Main(string[] args)
{
string OrderNo = 123;
MethodHelper.ModifyAppConfig(OrderNo);
}
}
MethodHelper.cs
----------
public static void ModifyAppConfig(string value)
{
try
{
Configuration config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
config.AppSettings.Settings["OrderNumber"].Value = value;
Thread.Sleep(TimeSpan.FromSeconds(3)); // added this so there's time for the file to be updated, not sure if necessary.
config.Save();
ConfigurationManager.RefreshSection("appSettings");
}
catch (System.IO.IOException e)
{
Console.WriteLine(e.Message + " key value passed for App Config: " + value);
}
}
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17 Comments
Active 4 days ago
which line gives you the error?
I think the issue is that there is no entry for OrderNumber and it needs to be created first
I think the issue is that there is no entry for OrderNumber and it needs to be created first
Active 4 days ago
try something like
I think the issue is that when you run it the first time, the entry for orderNumber is not there yet, so config.AppSettings.Setting
Actually replace
config.AppSettings.Settings.Add("OrderNumber", value);
I think the issue is that when you run it the first time, the entry for orderNumber is not there yet, so config.AppSettings.Setting
Actually replace
config.AppSettings.Settings["OrderNumber"].Value = value;
if(config.AppSettings.Settings["OrderNumber"]!=null)
config.AppSettings.Settings["OrderNumber"].Value = value;
else
config.AppSettings.Settings.Add("OrderNumber", value);
Active 4 days ago
Can you debug it?
Also you could make it write detailed errors to the log so you could have al'the details whenever the error occurs
Also you could make it write detailed errors to the log so you could have al'the details whenever the error occurs
Active 4 days ago
wrap your code in try...catch:
and make sure you add "using System.IO" at the top of your code file.
The code above is not tested as I don't have access to Visual studio at the moment so you might need some tweaks
try {
if(config.AppSettings.Settings["OrderNumber"]!=null)
config.AppSettings.Settings["OrderNumber"].Value = value;
else
config.AppSettings.Settings.Add("OrderNumber", value);
} catch (Exception ex) {
string path=Path.Combine(Application.StartUp, "myLog.txt");
if (! File.Exists(path))
File.Create(path);
using (StreamWriter w = File.AppendText(path))
{
w.WriteLine(ex.Message + ":" + ex.StackTrace);
}
}
and make sure you add "using System.IO" at the top of your code file.
The code above is not tested as I don't have access to Visual studio at the moment so you might need some tweaks
So i couldnt get your code to work but here's some new interesting finds.
When I open up the config file - the keys exist
<add key="OrderNumber" value="5924524" />
Then I decided to remove the key from the app config file and run the app and it still works and rewrites because it's not there as expected.
So it's mainly when the computer first reboots and runs the app for the first time and it fails when writing to the app config file. That is so strange - because it will fail with the same error whether or not the Order Number key exists!
Thoughts? Could it be related to security upon rebooting?
When I open up the config file - the keys exist
<add key="OrderNumber" value="5924524" />
Then I decided to remove the key from the app config file and run the app and it still works and rewrites because it's not there as expected.
So it's mainly when the computer first reboots and runs the app for the first time and it fails when writing to the app config file. That is so strange - because it will fail with the same error whether or not the Order Number key exists!
Thoughts? Could it be related to security upon rebooting?
Active 4 days ago
try adding this line
after
ConfigurationManager.RefreshSection("appSettings");
after
Configuration config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
Since the write log didnt' work, I just reverted it back.
Here's my current code:
Here's my current code:
Configuration config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
ConfigurationManager.RefreshSection("appSettings");
try
{
if (config.AppSettings.Settings["OrderNumber"] != null)
config.AppSettings.Settings["OrderNumber"].Value = value;
else
config.AppSettings.Settings.Add("OrderNumber", value);
config.Save();
ConfigurationManager.RefreshSection("appSettings");
}
catch (Exception e)
{
Console.WriteLine(e.Message + " key value passed for App Config: " + value);
}
Active 4 days ago
try this:
public static void ModifyAppConfig(string value)
{
Configuration config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
ConfigurationManager.RefreshSection("appSettings");
try
{
if (config.AppSettings.Settings["OrderNumber"] != null)
config.AppSettings.Settings["OrderNumber"].Value = value;
else
config.AppSettings.Settings.Add("OrderNumber", value);
config.Save(ConfigurationSaveMode.Modified);
ConfigurationManager.RefreshSection("appSettings");
}
catch (Exception e)
{
string filePath = @"C:\Error.txt";
using (StreamWriter writer = new StreamWriter(filePath, true))
{
writer.WriteLine("Message :" + e.Message + "<br/>" + Environment.NewLine + "StackTrace :" + e.StackTrace +
"" + Environment.NewLine + "Date :" + DateTime.Now.ToString() + Environment.NewLine);
}
}
}
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