用户控件数据绑定第一次不起作用

Question

myUserControl contains two control. A textbox and a lable. This usercontrol is in a class library porject. It will be used in several other projects.

I will just bind like this.

myControl1.Databindings.Add("DataSource",myObject,"PropertyName");

Here, PropertyName will directly bind with the textbox (Which I am successfull) and I have defined an attribute in myObject to get the label name using PropertyName . So While the userControl is setting label and textbox, it needs the whole binding to bind both label and textbox data.

What I have done is here (in Control):

private object dataSource;
    [DefaultValue("")]
    public Object DataSource
    {
        get
        {
            return dataSource;
        }
        set
        {
            dataSource = value;

            OnPropertyChanged(new PropertyChangedEventArgs("DataSource"));
            BindControls();
            if (dataSource != null)
            {
                textBox1.Text = dataSource.ToString();
            }

        }
    }

    //Method to bind datasource with controls
    public void BindControls()
    {
        if (this.DataBindings.Count > 0)
        {
            //Get the instance of the binded object
            object myObj = this.DataBindings[0].DataSource as object;

            //Get binded field name as string
            string bindingField = this.DataBindings[0].BindingMemberInfo.BindingField;

            //Get Type of the binded object
            Type t1 = myObj.GetType();

            //Get property information for the binded field
            PropertyInfo property = t1.GetProperty(bindingField);

            //Get text value for label
            LabelText = property.GetAttribute<DisplayNameAttribute>(false).DisplayName;
            textBox1.ForeColor = Color.Black;
            //If textbox data is null or empty, get descrition or comment as the textbox text.
            if (string.IsNullOrEmpty(dataSource.ToString()))
            {
                dataSource = property.GetAttribute<DescriptionAttribute>(false).Description;
                textBox1.ForeColor = Color.DarkGray;
            }
        }
    }

For the first time when I am binding the DataSource from FORM where I am using this control, The label text is empty though textbox contains the correct value. The reason I have found, The DataBinding Remains empty.

In My form, I have used a checkbox to switch the object values. And when I check the value, Usercontrol gets the databinding and everything then on goes right.

Answer 1

The problem is in the propertychange you are raising. The string should be same as the property name. Try something like this...

 public string Name
        {
            get { return m_Name; }
            set
            {
                if (m_Name != value)
                {
                    m_Name = value;
                    OnChange("Name");
                }
            }
        }