I have a Winforms app that I am developing
in C# that will serve as a frontend for a SQL Server 2005 database. I rolled
the executable out to a test machine
and ran it. It worked perfectly fine on
the test machine up until
the last round of changes that I made. However, now on
the test machine, it throws
the following exception immediately upon opening:
System.NullReferenceException: Object reference not set to an instance of an object.
at PSRD_Specs_Database_Administrat.mainMenu.mainMenu_Load(Object sender, EventArgs e)
at System.Windows.Forms.Form.OnLoad(EventArgs e)
at System.Windows.Forms.Form.OnCreateControl()
at System.Windows.Forms.Control.CreateControl(Boolean fIgnoreVisible)
at System.Windows.Forms.Control.CreateControl()
at System.Windows.Forms.Control.WmShowWindow(Message& m)
at System.Windows.Forms.Control.WndProc(Message& m)
at System.Windows.Forms.ScrollableControl.WndProc(Message& m)
at System.Windows.Forms.ContainerControl.WndProc(Message& m)
at System.Windows.Forms.Form.WmShowWindow(Message& m)
at System.Windows.Forms.Form.WndProc(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
The only thing that I changed
in this version that pertains to mainMenu_Load
is the way that
the connection
string to
the database
is called. Previously, I had set a
string with
the connection
string on every form that I needed to call it from, like:
string conString = "Data Source = SHAREPOINT;Trusted_Connection = yes;" +
"database = CustomerDatabase;connection timeout = 15";
As my app grew
and I added forms to it, I decided to add an App.config to
the project. I defined
the connection
string in it:
<connectionStrings>
<add name="conString"
providerName="System.Data.SqlClient"
connectionString="Data Source = SHAREPOINT;Trusted_Connection = yes;database = CustomerDatabase;connection timeout = 15" />
</connectionStrings>
I then created a static
string that would return
the conString:
public static
string GetConnectionString(string conName)
{
string strReturn =
string.Empty;
if (!(string.IsNullOrEmpty(conName)))
{
strReturn = ConfigurationManager.ConnectionStrings[conName].ConnectionString;
}
else
{
strReturn = ConfigurationManager.ConnectionStrings["conString"].ConnectionString;
}
return strReturn;
}
I removed
the conString variable
and now call
the connection
string like so:
PublicMethods.GetConnectionString("conString").ToString()
It appears that this
is giving me
the error. I changed these instances to directly call
the connection
string from App.config without using GetConnectionString. For instance,
in a SQLConnection:
using (SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["conString"].ConnectionString))
This also threw
the exception. However, when I went back to using
the conString variable on each form, I had no issues.
What I don't understand
is why all three methods work fine on my development machine, while using
the App.config directly or via
the static
string I created throw exceptions.
