c# - Warning "Fields .... is never assigned to and will always have its default value null"

Question

I am trying to insert the data into the database but the values inserted in the database are displayed null. There are also warnings like "Fields (x) is never assigned to and will always have its default value null" ( x = response1, response2, response3, response4, response5)

private void YesOrNoChecked(RadioButton radioButtonYes, RadioButton radioButtonNo,string response,int questionNo)
        {
            if (radioButtonYes.Checked)
            {
                response = "Yes";
            }
            else if (radioButtonNo.Checked)
            {
                response = "No";
            }
            else
            {
                MessageBox.Show("Question " + questionNo + " is not answered", "Message", MessageBoxButtons.OK, MessageBoxIcon.Warning);
                isChecked = false;
            }
        }

private void SatisfactionChecked(RadioButton rdoVerySatisfied, RadioButton rdoSatisfied, RadioButton rdoNeutral, 
            RadioButton rdoDissatisfied, RadioButton rdoVeryDissatisfied,string response,int questionNo)
        {
            if (rdoVerySatisfied.Checked)
            {
                response = "Very Satisfied";
            }
            else if (rdoSatisfied.Checked)
            {
                response = "Satisfied";
            }
            else if (rdoNeutral.Checked)
            {
                response = "Neutral";
            }
            else if (rdoDissatisfied.Checked)
            {
                response = "Dissatisfied";
            }
            else if (rdoVeryDissatisfied.Checked)
            {
                response = "Very Dissatisfied";
            }
            else
            {
                MessageBox.Show("Question " + questionNo + " is not answered", "Message", MessageBoxButtons.OK, MessageBoxIcon.Warning);
                isChecked = false;
            }
        } 

I called the functions...

    YesOrNoChecked(rdoYes1, rdoNo1, response1, 1); 
    YesOrNoChecked(rdoYes2, rdoNo2, response2, 2);  
    SatisfactionChecked(rdoVerySatisfied3, rdoSatisfied3, rdoNeutral3, rdoDissatisfied3, rdoVeryDissatisfied3, response3, 3);
    SatisfactionChecked(rdoVerySatisfied4, rdoSatisfied4, rdoNeutral4, rdoDissatisfied4, rdoVeryDissatisfied4, response4, 4);  
    SatisfactionChecked(rdoVerySatisfied5, rdoSatisfied5, rdoNeutral5, rdoDissatisfied5, rdoVeryDissatisfied5, response5, 5); 

I insert the data into the database

consumerResponsesTableAdapter.InsertConsumerResponses(lblSurveyDate.Text,
                        consumerID, ConsumerMenu.surveyID, response1, response2, response3, response4, response5, response6);

Is there any way to fix this?

question from:https://stackoverflow.com/questions/65939211/warning-fields-is-never-assigned-to-and-will-always-have-its-default-value

Answer 1

You seem to be under the misunderstanding that if you assign a value to a C# method parameter, that the value will affect the variable passed as that parameter by the calling method. In pass-by-value semantics this is not the case.

You wrote:

    private void YesOrNoChecked(RadioButton radioButtonYes, RadioButton radioButtonNo,string response, ...)
    {
        if (radioButtonYes.Checked)
        {
            response = "Yes";
        }

You might call it like:

string x = "x";
YesOrNoChecked(rb1, rb2, x, ...);

But x will never, ever have "Yes" or "No" in it, it will always only ever have "x" in it.

The reason for this is because, even though x and response start out referring to the same thing when you call the method (they both refer to "x") your assigning response = "Yes" makes a new thing ("Yes") leaving x pointing to the old thing ("x"), then when the method finishes, response is deleted, so the "Yes" is lost, and x always only ever pointed to "x"

In steps:
x --> "x"                               Before you call the method
x --> "x" <-- response                  As soon as you call the method
x --> "x"     response --> "Yes"        During the method
x --> "x"     response --> (is lost)    After the method finishes

---

To get it to work like that, you could use out modifier but I wouldn't recommend it (there are nearly never any reasons to use out parameters in C#). Instead, modify your methods to return the "Yes" or "No" and capture it when you call the method:

    private string YesOrNoChecked(RadioButton radioButtonYes, RadioButton radioButtonNo)
    {
        if (radioButtonYes.Checked)
        {
            return "Yes";
        }

and use it like:

string x = YesOrNoChecked(rb1,rb2);