C# pass value to dll

13y6.1kVisual Basic .NET

I have a C# 2010 desktop application that will be calling a dll. The dll is code that is to be shared between different application. I want to be able to pass database connection values to the app.config file in the dll.

Thus can you show me and/or explain to me how to accomplish this goal?

5 Replies

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Vulpes13y ago
Accepted answer
1. No, the program that calls the dll doesn't need a reference to System.Configuration.dll unless, of course, it's reading or writing to its own app.config file.

2. The dll can only have one app.config file. However, the file can contain multiple connection string settings each distinguished by its name. So each client of the dll can call the AddConnectionString method with its own settings. It would clearly be sensible to base the name of those settings on the name of the program calling the dll to ensure there are no clashes.

3. I don't understand this question. I didn't know the dll was calling another program and, even if it is, I don't see how it can have 4 app.config files unless you're using custom configuration files in addition to the default one?
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Vulpes13y ago
I imagine that, if the dll is calling into it, the solution file must itself be producing 4 separate dlls each with its own app.config file

In principle, each dll should update its own app.config file, and so I'd place a method similar to the one I included in my first post in each of the 4 project files but use a different name for the containing class.

Each of the 4 project files will, of course, need a reference to System.Configuration.dll but your dll will not require such a reference since (presumably) it is not now updating its own app.config file as I thought originally. Your dll will, though, require references to each of the 4 dlls themselves.

Your dll can still have its own AddConnectionString() method but all that will now do is to pass the parameters to the method in the appropriate dll.

I don't know whether the clients of your dll will know (or care) which of the 4 app.config files their connection details are to be stored in but, if they do, then perhaps you will need an additional parameter to indicate which one is to be used:

public static void AddConnectionString(int version, string name, string connectionString, string providerName)
{
switch(version)
{
case 1 :

Version1Class.AddConnectionString(name, connectionString, providerName);
break;

case 2 :

Version2Class.AddConnectionString(name, connectionString, providerName);
break;

case 3 :

Version3Class.AddConnectionString(name, connectionString, providerName);
break;

case 4 :

Version4Class.AddConnectionString(name, connectionString, providerName);
break;

default:

// incorrect version, take the appropriate action
break;
}
}
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scampercat13y ago
this is in response to, "I don't understand this question. I didn't know the dll was calling another program and, even if it is, I don't see how it can have 4 app.config files unless you're using custom configuration files in addition to the default one".

The program that is called in the dll has a solution file with 4 project files. Each project file has a app.config file. Thus there was a total of 4 app.config files.

Thus can a dll be setup to access a solution file that has 4 app.config files? If so, how can I access the specific app.config I need when accessing the solution file that has 4 app.config files? There is only one specific app.config file that I will probably need to access.

Can you show me code on how to access the specific app.config file in a specific project file?

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dc13y ago
I have the following items to mention:

1. you stated "You'll need to add a reference to System.Configuration.dll to your dll if you don't have one already." Will I need to add this reference in the program that calls the dll?

2. you stated, "You can then call this method from the client with code such as the following:
SomeClass.AddConnectionString (name, connectionString, providerName);" When I need to do this for each app.config file?

3. There are 4 app.config files in the program called by the dll. Thus can you tell me how to use the code you suggested for 4 app.config files?
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Vulpes13y ago
I'd add a public static method to a public class in your dll which adds connection string details to its app.config file.

A client of the dll can then call the method and pass the appropriate database connection values.

The code for the method will be something on these lines:

using System.Configuration;

// ....

public static void AddConnectionString(string name, string connectionString, string providerName)
{
// Get the configuration file.
Configuration config = ConfigurationManager.OpenExeConfiguration (ConfigurationUserLevel.None);

// Add the connection string.
ConnectionStringsSection csSection = config.ConnectionStrings;
ConnectionStringSettings csSettings = new ConnectionStringSettings(name, connectionString, providerName);
csSection.ConnectionStrings.Add(csSettings);

// Save the configuration file.
config.Save(ConfigurationSaveMode.Modified);
}

You'll need to add a reference to System.Configuration.dll to your dll if you don't have one already.

You can then call this method from the client with code such as the following:

SomeClass.AddConnectionString (name, connectionString, providerName);
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