Question how do i get value of combo box from one user control to another

[solutionsdxb]

Hi,

i am using vb.net 2005 to developed desktop application ,

I am having two windows form user control , the first control name con.vb containing the design and code for connecting to database and getting a list of my project values in combo box.

Now the second user control report.vb which i am using to generate some reports , since the code behind is using connection to connect to various project database , so i want to get the value of

First user control into another how i can get the i have tried the below but its giving me error in run time but no error in design or code behind -

MR.MainForm.Connection1.project_combobox.SelectedValue.ToString

Error i am getting is :

System.NullReferenceException was unhandled
Message="Object reference not set to an instance of an object."
Source="MDR"

 

[henryminute]

A NullReferenceException can occur if there is no item selected in your ComboBox.
To avoid this do something like:

    If Not MR.MainForm.Connection1.project_combobox.SelectedValue is Nothing Then
        MR.MainForm.Connection1.project_combobox.SelectedValue.ToString

 

[solutionsdxb]

but there is already selected itemin the combobox ,is it because of i am calling or using the combobox in the main form , could you pls. check my syntax is correct and how i am using the combobox in user control as this user control is inside the other user control.

with regards

 

[henryminute]

What you have to do is to discover which object instance is Nothing. When the error occurs move the mouse-pointer over each object reference in the offending line and wait for the tool-tip to appear. It will either give the value of the instance, or tell you it is Nothing.

I usually find that knowing which is the null instance makes me home in on the cause of the problem.

 

[BlackByte]

Maybe your reffering to values that don't exist. Because after the con.vb form is closed, the values you have put in the combobox are lost.