ConfigurationManager connection string is null in UserControl

Question

I have an application which gets data to the forms through a datalayer which uses something like this:

public DataTable get(String query, ArrayList parameters = null)
{            
   using (iDB2Connection cn =  new iDB2Connection(ConfigurationManager.ConnectionStrings["iseries"].ToString()))
   {
       // get the data and return them    
   }
}

I have forms which get data and this works fine.

However, I created a UserControl which gets data through this method which works fine when I run my project, however, the form which contains the UserControl throws a designer exception.

"To prevent possible data loss before loading the designer, the following errors must be resolved: "

I found that the error is located at the retrieval of the connection string from the <appSettings>.

It throws a nullpointerexception.

But only in design mode. When I ignore it, everything works fine, however, I would like to know how to resolve this.

Why are my <appSettings> null when accessing them through my UserControl?

UPDATE 1

It seems my UserControl doesn't recognize the <appSettings> at all.

When I put this code in my UserControl Load event I get a nullreference as well.

private void SelectUser_Load(object sender, EventArgs e)
{            
   txtLocation.Text = ConfigurationManager.AppSettings["location"].ToString();
}

Are you able to Read connection string value from any other place ? — Kurubaran
– Kurubaran, Commented May 22, 2014 at 6:37
Yes, everything works fine except for reading the values from a UserControl. In a "normal" form, I can read it perfectly. — randomizer
– randomizer, Commented May 22, 2014 at 8:14

randomizer · Accepted Answer · 2014-05-22 12:18:45Z

3

I found the solution, in designmode the usercontrol already executes the code in the Load-event. Because the App.config isn't available in designmode it isn't found and therefore not loaded. So I made a little check around it to check if in designmode or not:

bool designMode = (LicenseManager.UsageMode == LicenseUsageMode.Designtime);
if (designMode)
{
    string location = ConfigurationManager.AppSettings["location"].ToString();
}

answered May 22, 2014 at 12:18

randomizer

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Comments

ovaltein · Accepted Answer · 2014-05-21 14:09:00Z

0

I think you just need to tweak how you're fetching your ConnectionString.

using (iDB2Connection cn =  new iDB2Connection(ConfigurationManager.ConnectionStrings["iseries"].ConnectionString)
{
    //get the data and return them    
}

answered May 21, 2014 at 14:09

ovaltein

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1 Comment

randomizer Over a year ago

Nope, still getting "Object reference not set to an instance of an object." ConfigurationManager settings are null in a usercontrol for some reason.

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