I want to populate my combo box with values from my XML file (which I have done), and then display some elements under that values tree in labels. Everything is in a tab page
I've created combo boxes like this in my button click:
int i = 0; //global variable for keeping track of combo box objects
int j = 0; // same but for labels
//the following codes are in the button click:
var document = XDocument.Load(workingDir + @"\Level4.xml");
comboBoxModuleSelect.Add(new ComboBox());
System.Drawing.Point p = new System.Drawing.Point(7, 57 + i * 25);
(comboBoxModuleSelect[i] as ComboBox).Location = p;
(comboBoxModuleSelect[i] as ComboBox).Size = new System.Drawing.Size(183, 20);
tabPageLevel4.Controls.Add(comboBoxModuleSelect[i] as ComboBox);
and populated them like this:
var moduleName = from d in document.Descendants("moduleTitle")
select d.Value;
foreach (var item in moduleName)
{
//add the module names into the dropdown for students to select
(comboBoxModuleSelect[i] as ComboBox).Items.Add(item);
}
Now I want to take the selected value in the current combo box which is selected by the user and retrieve some XML elements related to that value. However I'm getting a NullReferenceException in this line:
var assessment = from d in document.Descendants("moduleTitle")
where d.Value == (comboBoxModuleSelect[i] as ComboBox).SelectedItem.ToString()
select d.Parent.Element("assessmentType").Value;
on comboBoxModuleSelect[i]
The XML is as follows if that is needed:
<?xml version="1.0" encoding="utf-8" ?>
<Course>
<CourseName>BEng Software Engineering</CourseName>
<Modules>
<Module>
<moduleCode>ECSE401</moduleCode>
<moduleTitle>Programming Methodology</moduleTitle>
<credits>15</credits>
<assessmentDetails>
<assessment>
<assessmentName>Coursework</assessmentName>
<assessmentType>Coursework</assessmentType>
<assessmentWeighting>40</assessmentWeighting>
</assessment>
<assessment>
<assessmentName>Coursework</assessmentName>
<assessmentType>Coursework</assessmentType>
<assessmentWeighting>40</assessmentWeighting>
</assessment>
<assessment>
<assessmentName>Test2</assessmentName>
<assessmentType>Coursework</assessmentType>
<assessmentWeighting>30</assessmentWeighting>
</assessment>
</assessmentDetails>
</Module>
<Module>
<moduleCode>ECSC404</moduleCode>
<moduleTitle>Computer Systems Fundamentals</moduleTitle>
<credits>15</credits>
<assessmentDetails>
<assessment>
<assessmentName>Test1</assessmentName>
<assessmentType>Coursework</assessmentType>
<assessmentWeighting>30</assessmentWeighting>
</assessment>
<assessment>
<assessmentName>Test2</assessmentName>
<assessmentType>Coursework</assessmentType>
<assessmentWeighting>30</assessmentWeighting>
</assessment>
<assessment>
<assessmentName>Test3</assessmentName>
<assessmentType>Coursework</assessmentType>
<assessmentWeighting>40</assessmentWeighting>
</assessment>
</assessmentDetails>
</Module>
<Module>
<moduleCode>EBSY401</moduleCode>
<moduleTitle>Information and Data Modelling</moduleTitle>
<credits>15</credits>
<assessmentDetails>
<assessment>
<assessmentName>Test</assessmentName>
<assessmentType>Coursework</assessmentType>
<assessmentWeighting>25</assessmentWeighting>
</assessment>
<assessment>
<assessmentName>Coursework1</assessmentName>
<assessmentType>Coursework</assessmentType>
<assessmentWeighting>10</assessmentWeighting>
</assessment>
<assessment>
<assessmentName>Coursework2</assessmentName>
<assessmentType>Coursework</assessmentType>
<assessmentWeighting>35</assessmentWeighting>
</assessment>
<assessment>
<assessmentName>Coursework3</assessmentName>
<assessmentType>Coursework</assessmentType>
<assessmentWeighting>30</assessmentWeighting>
</assessment>
</assessmentDetails>
</Module>
<Module>
<moduleCode>ECSC405</moduleCode>
<moduleTitle>Software Development Principles</moduleTitle>
<credits>15</credits>
<assessmentDetails>
<assessment>
<assessmentName>Test1</assessmentName>
<assessmentType>Coursework</assessmentType>
<assessmentWeighting>30</assessmentWeighting>
</assessment>
<assessment>
<assessmentName>Coursework</assessmentName>
<assessmentType>Coursework</assessmentType>
<assessmentWeighting>40</assessmentWeighting>
</assessment>
<assessment>
<assessmentName>Test2</assessmentName>
<assessmentType>Coursework</assessmentType>
<assessmentWeighting>30</assessmentWeighting>
</assessment>
</assessmentDetails>
</Module>
<Module>
<moduleCode>ECSC407</moduleCode>
<moduleTitle>Web Technology</moduleTitle>
<credits>15</credits>
<assessmentDetails>
<assessment>
<assessmentName>Tutorials</assessmentName>
<assessmentType>Coursework</assessmentType>
<assessmentWeighting>20</assessmentWeighting>
</assessment>
<assessment>
<assessmentName>Coursework</assessmentName>
<assessmentType>Coursework</assessmentType>
<assessmentWeighting>20</assessmentWeighting>
</assessment>
<assessment>
<assessmentName>Exam</assessmentName>
<assessmentType>Exam</assessmentType>
<assessmentWeighting>60</assessmentWeighting>
</assessment>
</assessmentDetails>
</Module>
<Module>
<moduleCode>ECSC409</moduleCode>
<moduleTitle>Software Engineering Principles</moduleTitle>
<credits>15</credits>
<assessmentDetails>
<assessment>
<assessmentName>Test1</assessmentName>
<assessmentType>Coursework</assessmentType>
<assessmentWeighting>40</assessmentWeighting>
</assessment>
<assessment>
<assessmentName>Coursework1</assessmentName>
<assessmentType>Coursework</assessmentType>
<assessmentWeighting>30</assessmentWeighting>
</assessment>
<assessment>
<assessmentName>Coursework2</assessmentName>
<assessmentType>Coursework</assessmentType>
<assessmentWeighting>30</assessmentWeighting>
</assessment>
</assessmentDetails>
</Module>
<Module>
<moduleCode>ECSC408</moduleCode>
<moduleTitle>Mathematics for Computing</moduleTitle>
<credits>15</credits>
<assessmentDetails>
<assessment>
<assessmentName>Coursework</assessmentName>
<assessmentType>Coursework</assessmentType>
<assessmentWeighting>50</assessmentWeighting>
</assessment>
<assessment>
<assessmentName>Exam</assessmentName>
<assessmentType>Exam</assessmentType>
<assessmentWeighting>50</assessmentWeighting>
</assessment>
</assessmentDetails>
</Module>
<Module>
<moduleCode>EBSY400</moduleCode>
<moduleTitle>Communication and Learning Skills</moduleTitle>
<credits>15</credits>
<assessmentDetails>
<assessment>
<assessmentName>Presentation</assessmentName>
<assessmentType>Coursework</assessmentType>
<assessmentWeighting>30</assessmentWeighting>
</assessment>
<assessment>
<assessmentName>Portfolio</assessmentName>
<assessmentType>Coursework</assessmentType>
<assessmentWeighting>70</assessmentWeighting>
</assessment>
</assessmentDetails>
</Module>
</Modules>
</Course>
Why am I getting a nullreferenceexception?
Try changing .SelectedItem.ToString() to . Text as comboBox_type_boat.Text returns the selected value The SelectedItem.ToString() dosent return the value for comboboxes popluated from XML
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