当复选框仍处于选中状态时，将消息保留在文本框中

Question

I have 3 checkboxes with corresponding message in a textbox. My teacher wants the message to remain in the textbox when the checkbox is still checked and hide the text when it is unchecked. In my case when I checked the 3 checkboxes their 3 corresponding messages will appear but when I unchecked one of the checkboxes and the other two are still checked, all the message will disappear. My problem is when I unchecked one of the checkbox and and the other 2 are still checked the corresponding messages with the remaining two checked checkboxes will remain in their textboxes.

private void chkCarWheels_CheckedChanged(object sender, EventArgs e)
{
    if (chkCarWheels.Checked == true)
        lblMessage.Text = lblMessage.Text + mycar.hasWheels(4);
    else
        lblMessage.Text = "My  " + txtName.Text + " Car";
}

private void chkCarAcceleration_CheckedChanged(object sender, EventArgs e)
{
    if (chkCarAcceleration.Checked == true)
       lblMessage.Text = lblMessage.Text + mycar.Accelerate();
    else
        lblMessage.Text = "My  " + txtName.Text + " Car";
} 

private void chkCarBreakpad_CheckedChanged(object sender, EventArgs e)
{
    if (chkCarBreakpad.Checked == true)
        lblMessage.Text = lblMessage.Text + mycar.hasBreak();
    else
        lblMessage.Text = "My  " + txtName.Text + " Car";
}

Answer 1

Looks like you need to create message depending on checkboxes states. You can create method, which will do the job and call it when state of some checkbox changed.

private void chkCarWheels_CheckedChanged(object sender, EventArgs e)
{
    BuildMessage();
}

private void chkCarAcceleration_CheckedChanged(object sender, EventArgs e)
{
    BuildMessage();
} 

private void chkCarBreakpad_CheckedChanged(object sender, EventArgs e)
{
    BuildMessage();
}

Or the better one - create one event handler for all checkboxes :

// use for chkCarWheels, chkCarAcceleration, chkCarBreakpad
private void chkCar_CheckedChanged(object sender, EventArgs e)
{
    BuildMessage();
}

private void BuildMessage()
{     
    lblMessage.Text = "My  " + txtName.Text + " Car";
    if (chkCarWheels.Checked)
        lblMessage.Text = lblMessage.Text + mycar.hasWheels(4);
    if (chkCarAcceleration.Checked)
       lblMessage.Text = lblMessage.Text + mycar.Accelerate();
    if (chkCarBreakpad.Checked)
       lblMessage.Text = lblMessage.Text + mycar.hasBreak();
}

You don't need to compare boolean values with true/false. Use those values directly if (chkCarWheels.Checked) . And keep in mind that in C# we use CamelCase names form methods. Also consider to use StringBuilder to build whole message and then assign it to label:

private void BuildMessage()
{
    StringBuilder sb = new StringBuilder();
    sb.AppendFormat("My {0} Car", txtName.Text);
    if (chkCarWheels.Checked)
        sb.Append(mycar.hasWheels(4));
    if (chkCarAcceleration.Checked)
       sb.Append(mycar.Accelerate());
    if (chkCarBreakpad.Checked)
       sb.Append((mycar.hasBreak());
    lblMessage.Text = sb.ToString();
} 

Answer 2

Try this:

    private void chkCarWheels_CheckedChanged(object sender, EventArgs e)
    {
        chkCar();
    }

    private void chkCarAcceleration_CheckedChanged(object sender, EventArgs e)
    {
        chkCar();
    } 

    private void chkCarBreakpad_CheckedChanged(object sender, EventArgs e)
    {
       chkCar()
    } 



private void chkCar()
{

string msg="";

if (chkCarWheels.Checked)
msg=msg+mycar.hasWheels(4);

if(chkCarAcceleration.Checked)
msg=msg+mycar.Accelerate();

if(chkCarBreakpad.Checked)
msg=msg+mycar.hasBreak();

lblMessage.Text=msg;

}