How to add values of combobox to database?

Question

In the collection of my BloodType combobox property. I have 3 values which is O, A and C. But after I choose the option of the value I want, and click submit I get this error.

The parameterized query '(@pFirstName nvarchar(5),@pLastName nvarchar(6),@pContact nvarch' expects the parameter '@pBloodType', which was not supplied.

It will worked if I use a textbox for my bloodtype instead.

For my textbox code which is before.

updateCmd.Parameters.AddWithValue("@pBloodType", txtpBloodType.Text);

For comboBox code which i am using now.

updateCmd.Parameters.AddWithValue("@pBloodType", cbpBloodType.SelectedValue);

enter image description here

Still Object reference not set to an instance of an object.

enter image description here

   public patient()
    {
        InitializeComponent();
        this.cbpBloodType = new System.Windows.Forms.ComboBox();
        this.cbpBloodType.Items.Add("O");
        this.cbpBloodType.Items.Add("A");
        this.cbpBloodType.Items.Add("C");
    }

    private int AddPatientRecord()
    {
        int result = 0;
        // TO DO: Codes to insert customer record
        //retrieve connection information info from App.config
        string strConnectionString = ConfigurationManager.ConnectionStrings["SACPConnection"].ConnectionString;
        //STEP 1: Create connection
        SqlConnection myConnect = new SqlConnection(strConnectionString);
        //STEP 2: Create command
        String strCommandText = "INSERT PATIENT(pFirstName, pLastName, pContact, pAddress, pCity, pZip, pNationality, pRace, pIC, pGender, pDOB, pBloodType, pEmail) "
            + " VALUES (@pFirstName,@pLastName,@pContact,@pAddress,@pCity,@pZip,@pNationality, @pRace, @pIC, @pGender, @pDOB, @pBloodType, @pEmail)";

        SqlCommand updateCmd = new SqlCommand(strCommandText, myConnect);

        updateCmd.Parameters.AddWithValue("@pFirstName", txtpFirstName.Text);
        updateCmd.Parameters.AddWithValue("@pLastName", txtpLastName.Text);
        //updateCmd.Parameters["@clientid"].Direction = ParameterDirection.Output; 
        updateCmd.Parameters.AddWithValue("@pContact", txtpContact.Text);
        updateCmd.Parameters.AddWithValue("@pAddress", txtpAddress.Text);
        updateCmd.Parameters.AddWithValue("@pCity", txtpCity.Text);
        updateCmd.Parameters.AddWithValue("@pZip", txtpZip.Text);
        updateCmd.Parameters.AddWithValue("@pNationality", txtpNationality.Text);
        updateCmd.Parameters.AddWithValue("@pRace", txtpRace.Text);
        updateCmd.Parameters.AddWithValue("@pIC", txtpIC.Text);
        if (rbMale.Checked)
        {
            updateCmd.Parameters.AddWithValue("@pGender", "M");
        }
        else
        {
            updateCmd.Parameters.AddWithValue("@pGender", "F");
        }
        updateCmd.Parameters.AddWithValue("@pDOB", dtppDOB.Value);
        string value = cbpBloodType.SelectedItem == null ? "A" : cbpBloodType.SelectedItem.ToString();
        updateCmd.Parameters.AddWithValue("@pBloodType", value);
        updateCmd.Parameters.AddWithValue("@pEmail", txtpEmail.Text);
        // STEP 3 open connection and retrieve data by calling ExecuteReader
        myConnect.Open();
        // STEP 4: execute command
        // indicates number of record updated.
        result = updateCmd.ExecuteNonQuery();

        // STEP 5: Close
        myConnect.Close();
        return result;

    }

have you tried using updateCmd.Parameters.AddWithValue("@pBloodType", cbpBloodType.SelectedValue.ToString()); ? calling the ToString() method on the value? — CuccoChaser
– CuccoChaser, Commented Jan 27, 2014 at 14:33
Did you check in the debugger that cbpBloodType and cbpBloodType.SelectedValue exist when running your code? — Plue
– Plue, Commented Jan 27, 2014 at 14:37

Plue · Accepted Answer · 2014-01-27 16:35:02Z

1

Try to initialize your combobox in code behind :

public Form1()
{
    InitializeComponent();
    cb1.Items.Add("O");
    cb1.Items.Add("A");
    cb1.Items.Add("C");
}

Then access the data with cbpBloodType.SelectedItem.ToString();

string value = cbpBloodType.SelectedItem == null ? "A" : cbpBloodType.SelectedItem.ToString();
updateCmd.Parameters.AddWithValue("@pBloodType", value);

edited Jan 27, 2014 at 16:35

answered Jan 27, 2014 at 15:30

Plue

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10 Comments

Pony Over a year ago

omg this worked, but whatever i clicked, it always gives me A in the datagrid @Plue

Pony Over a year ago

must be this line of code. // Pass default value, for example A updateCmd.Parameters.AddWithValue("@pBloodType", "A"); . how to rewrite it? @Plue

Plue Over a year ago

Change string bloodtype = cbpBloodType.Text; to string bloodtype = cbpBloodType.SelectedValue;

Pony Over a year ago

I got error when changed to that . Error 2 Cannot implicitly convert type 'object' to 'string'. An explicit conversion exists (are you missing a cast?) @Plue

Pony Over a year ago

After changed to this. string bloodtype = cbpBloodType.SelectedValue.ToString(); this error again. Object reference not set to an instance of an object. @Plue

|

user123456 · Accepted Answer · 2014-01-27 14:42:35Z

0

Mybe cbpBloodType.SelectedValue return null. How are you binding your drop downlist ?

Try this

private int AddPatientRecord()
{
    int result = 0;
    // TO DO: Codes to insert customer record
    //retrieve connection information info from App.config
    string strConnectionString = ConfigurationManager.ConnectionStrings["SACPConnection"].ConnectionString;
    //STEP 1: Create connection
    SqlConnection myConnect = new SqlConnection(strConnectionString);
    //STEP 2: Create command
    String strCommandText = "INSERT PATIENT(pFirstName, pLastName, pContact, pAddress, pCity, pZip, pNationality, pRace, pIC, pGender, pDOB, pBloodType, pEmail) "
        + " VALUES (@pFirstName,@pLastName,@pContact,@pAddress,@pCity,@pZip,@pNationality, @pRace, @pIC, @pGender, @pDOB, @pBloodType, @pEmail)";

    SqlCommand updateCmd = new SqlCommand(strCommandText, myConnect);

    updateCmd.Parameters.AddWithValue("@pFirstName", txtpFirstName.Text);
    updateCmd.Parameters.AddWithValue("@pLastName", txtpLastName.Text);
    //updateCmd.Parameters["@clientid"].Direction = ParameterDirection.Output; 
    updateCmd.Parameters.AddWithValue("@pContact", txtpContact.Text);
    updateCmd.Parameters.AddWithValue("@pAddress", txtpAddress.Text);
    updateCmd.Parameters.AddWithValue("@pCity", txtpCity.Text);
    updateCmd.Parameters.AddWithValue("@pZip", txtpZip.Text);
    updateCmd.Parameters.AddWithValue("@pNationality", txtpNationality.Text);
    updateCmd.Parameters.AddWithValue("@pRace", txtpRace.Text);
    updateCmd.Parameters.AddWithValue("@pIC", txtpIC.Text);
    if (rbMale.Checked)
    {
        updateCmd.Parameters.AddWithValue("@pGender", "M");
    }
    else
    {
        updateCmd.Parameters.AddWithValue("@pGender", "F");
    }
    updateCmd.Parameters.AddWithValue("@pDOB", dtppDOB.Value);
    if(!String.IsNullOrEmpty(cbpBloodType.SelectedValue.ToString()))
    {
      updateCmd.Parameters.AddWithValue("@pBloodType", cbpBloodType.SelectedValue.ToString());
    }
    else
    {
       // Pass default value, for example A
       updateCmd.Parameters.AddWithValue("@pBloodType","A");
    } 
    updateCmd.Parameters.AddWithValue("@pEmail", txtpEmail.Text);
    // STEP 3 open connection and retrieve data by calling ExecuteReader
    myConnect.Open();
    // STEP 4: execute command
    // indicates number of record updated.
    result = updateCmd.ExecuteNonQuery();

    // STEP 5: Close
    myConnect.Close();
    return result;

}

answered Jan 27, 2014 at 14:42

user123456

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9 Comments

Pony Over a year ago

I got this Object reference not set to an instance of an object by following your code @Mohammad jouhari

Pony Over a year ago

So now instead of writing it in the collection in the property. I write the values in the code is it? @Mohammad jouhari

user123456 Over a year ago

Where you got exactly the Object reference not set to an instance of an object ? Can you Debug It ?

user123456 Over a year ago

I thing you have issue with binding the drop down list. Can you share with us that code ?

Martin Smellworse Over a year ago

At least put your connection to the database in a try catch so you definitely close the connection if the database doesn't like what you send it. Your code is begging for a database connection to be left open.

|

K.DW · Accepted Answer · 2014-01-27 15:19:01Z

0

Not sure why the null exception but in any case I bet you are getting the wrong value from "Selected Value". Assign the variable first then step through it. I bet you might find you are not getting back "A" or "B" but rather something like "System.Windows.Controls..."

try this and see if you get the same error.

string bloodtype = cbpBloodType.Text;

if(!String.IsNullOrEmpty(bloodtype))

edited Jan 27, 2014 at 15:19

answered Jan 27, 2014 at 15:13

K.DW

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1 Comment

K.DW Over a year ago

And when you step through it, is the variable getting assigned properly or is the error happening when you call the AddWithValue?

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