Problem With displaying List<t> in datagrid?

Question

I have a class named Result which has 4 fields as id, marks, total, avg . I created the List class and stored the result.

Now I want to display only 2 columns in the datagrid. They are id and total . I successfully displayed the id and total but the datagrid shows 4 columns instead of 2. The columns are id, total, id, total

Here is my code to display the datagrid:

private void Form1_Load(object sender, EventArgs e)
    {
        List<Result> result = new List<Result>();
        PopulateResult();
        dgresult.AutoGenerateColumns = false;
        dgresult.Items.Clear();
        dgresult.ItemsSource = result;
        DataGridTextColumn col1 = new DataGridTextColumn();
        col1.Header = "Id";
        col1.Binding = new Binding("Id");
        DataGridTextColumn col2 = new DataGridTextColumn();
        col2.Header = "Total";
        col2.Binding = new Binding("Total");
        dgresult.Columns.Add(col1);
        dgresult.Columns.Add(col2);
    }
}
class Result
{
    int id;
    int total;
    int marks;
    int avg;

    public int Id { get { return id; } set { id = value; } }
    public int Total { get { return total; } set { total = value; } }
    public int Marks { get { return marks; } set { marks = value; } }
    public int Avg { get { return avg; } set { avg = value; } }

    public Result(int ID, int TOTAL, int MARKS, int AVG)
    {
        id = ID;
        total = TOTAL;
        marks = MARKS;
        avg = AVG;
    }
}

I don't understand why it is happening like this.

Thanks in advance.

Answer 1

I've added comments to your code that show my thoughts:

private void Form1_Load(object sender, EventArgs e)
{
    // Make a new list of result class objects, local to the Form1_Load method:
    List<Result> result = new List<Result>();

    // Call a method that populates a list... wait, what list?
    PopulateResult();

    dgresult.AutoGenerateColumns = false;
    dgresult.Items.Clear();

    // Set the datagrid data source to the list created earlier
    dgresult.ItemsSource = result;
    // ...

I'm not sure why the datagrid has a duplicate set of columns after you've specified and added only two columns. It would help to see the method PopulateResult() .

The list that PopulateResult() is adding to must be some other list, because the one created in Form1_Load is local in scope.

I'm not sure if this is just a little oversight, or if you need to learn about variable scope. Forgive me if this is already known to you:

• C# Variable Scopes