CODEWITHSUNDEEP
c#user-controlsinitialization
John
John

Reputation: 16007

Why isn't my UserControl keeping its initialization?

I have a UserControl for which I think I'm initializing some of the members:

// MyUserControl.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Drawing;
using System.Data;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace MyNamespace
{
    public partial class MyUserControl : UserControl
    {
        private string m_myString;
        private int m_myInt;

        public string MyString
        {
            get { return m_myString; }
            set { m_myString = value; }
        }
        public int MyInt
        {
            get { return m_myInt; }
            set { m_myInt = value; }
        }

        public MyUserControl()
        {
            InitializeComponent();

            MyString = "";   // was null, now I think it's ""
            MyInt = 5;       // was 0, now I think it's 5
        }

        // .........
    }
}

When I insert this control into my main form, though, and call a function that checks values within MyUserControl, things don't look like they're initialized:

// MainForm.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace MyProgram
{
    public partial class MainForm : Form
    {
        public MainForm()
        {
            InitializeComponent();
        }

        private void MyButton_Click(object sender, EventArgs e)
        {
            // this prints 0 rather than 5
            MessageBox.Show(this.theUserControl.MyInt.ToString());
        }
    }
}

I'm guessing this is a really simple error but I don't know where. I've tried prepending this. to things, but this probably isn't the way to go about fixing code. :)

Thanks as always!

EDIT: Stepping into the designer code as Pete suggested showed me where the write-over was happening. First I called the constructor of the user control, and then later, the values got overwritten with default values. I hadn't specified any default values (Sanjeevakumar Hiremath's suggestion) so the default values were those of the primitive types (for int this was 0).

Upvotes: 0

Views: 323

Answers (2)

JaredPar
JaredPar

Reputation: 754565

What you're likely seeing here is an artifact of the designer. If you ever opened up MainForm in a designer after you added MyUserControl it likely recorded the default values of MyUserControl in the generated InitializeComponent method of MainForm. These recorded values are re-assigned after the constructor of MyUserControl runs hence they're overwriting the values you set.

You can control this behavior via the use of the DesignerSerializationVisibilityAttribute

Upvotes: 3

Sanjeevakumar Hiremath
Sanjeevakumar Hiremath

Reputation: 11263

Use [DefaultValue] Attribute. It lets you specify default value for a property of a control when the value is not specified in the designer.

Upvotes: 2

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