how to check if staffid exist before saving

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I have a form which stores staff records. I want the form to check in sql db to
see if a staff id exists and display "The Staff ID Already Exist" instead of the
normal error message "violation of primary constraint ...." when the save button is
clicked. I tried this but it only checks for the first row in the table but if the staffid
is in the subsequent rows it displays the normal error message.

Please help me out.

Code behind form:

C#

private void btnSave_Click(object sender, EventArgs e)
        {

            SqlConnection conn = new SqlConnection(ConfigurationSettings.AppSettings["ConnectionString"]);
            conn.ConnectionString = "Data Source=MICKY-PC;Initial Catalog=SMS;User ID=sa;Password=mike";
            conn.Open();
            
            //save data
            try
            {
                if (!validateScreen())
                    return;
                clsStaffpersonal person = new clsStaffpersonal();
                             
                SqlCommand cmd = new SqlCommand("SELECT * FROM tblstaffpersonaldetails", conn);

                SqlDataReader dr = cmd.ExecuteReader();

            if (dr.Read())
            {
                if (this.txtStaffid.Text != dr["staffid"].ToString())
                {
                                    
                var
                _with1 = person;
                _with1.ID = this.txtStaffid.Text;
                _with1.myPicture = lblPicture.Text;
                _with1.entitle = cboTitle.Text;
                _with1.Sname = txtSurname.Text;
                _with1.Mname = txtMiddlename.Text;
                _with1.Fname = txtFirstname.Text;
                
                _with1.saveRegister();

                else
                {
                    MessageBox.Show("The Staff ID Already Exist");
                    return;
                }
            }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
        }

Code in class:

C#

public void saveRegister()
       {
           //saves the data in memory


           SqlCommand cmd = new SqlCommand();
           string dat = null;
           dat = dateofbirth.Year + "-" + dateofbirth.Month + "-" + dateofbirth.Day;
           string sqlQuery = null;
           sqlQuery = "Insert into tblstaffpersonaldetails values('" + staffid + "','" + title + "','" + surname + "','" + middlename + "','" + firstname + "','" + gender + "','" + dat + "','" + age + "','" + nationality + "','" + religion + "','" + maritalstatus + "','" + spousename + "','" + numberofchildren + "','" + emergencycontactnumber + "','" + residentialaddress + "','" + postaladdress + "','" + contactnumber + "','" + contactnumber2 + "','" + email + "','" + nameofnok + "','" + nokcontactnumber + "','" + idtype + "','" + idnumber + "','" + idexpirydate + "','" + picture + "')";
           // sqlQuery = "Insert into tblstaffpersonaldetails values('" + client_id + "',dbo.ProperCase('" + surname + "'),'" + othername + "','" + gender + "','" + dat + "','" + age + "','" + nationality + "','" + residential_address + "','" + postal_address + "','" + contact_number + "','" + marital_status + "','" + spouse_name + "','" + email + "','" + occupation + "','" + typeof_id + "','" + id_number + "','" + id_expirydate + "','" + remarks + "','" + picture + "','" + active_status + "')";


           cmd.Connection = conn;
           cmd.CommandText = sqlQuery;
           cmd.CommandType = System.Data.CommandType.Text;
           conn.Open();
           cmd.ExecuteNonQuery();
           cmd.Dispose();
           conn.Close();
       }

Posted 10-Jul-12 5:44am

mikeoabban

Updated 10-Jul-12 6:00am

R. Giskard Reventlov

v2

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Kiran Susarla · Answer 1 · 2012-07-10T06:07:00

In the btnSave_Click please modify as shown below

C#

...
SqlCommand cmd = new SqlCommand(string.Format("SELECT * FROM tblstaffpersonaldetails WHERE StaffId='{0}'", this.txtStaffid.Text), conn);
SqlDataReader dr = cmd.ExecuteReader();

if (dr.HasRows)
{
    // Id already present
}
else
{
    // Id is not present. So you can create a new record.
}

If the solution works please click like.

All the Best
Kiran

**R. Giskard Reventlov** · Answer 2 · 2012-07-10T06:15:00

You should do the insert through a stored procedure, passing parameters rather than constructing sql in code.

One way (of many) to do this is to wrap the process in a try/catch - transaction inside a stored procedure which, if it fails, returns a value that you can inspect and then take the appropriate action:

SQL

-- Wrap in try catch to return success/failure.
begin try

	-- Wrap in a transaction.
	begin tran

		-- Add new record.
		insert into Table (Field1, Field2, Field3)
		values (@Param1, @Param2, @Param3)

	-- Commit the transaction.
	commit tran

	-- If we get here it succeeded.
	select 1 [Result]

end try
begin catch

	-- Transaction failed?
	if @@trancount > 0
	begin
		-- Undo.
		rollback
	end

	-- Let the app know that it failed.
	select 0 [Result]

end catch

Another way might be to pass the staffid and test that with:

SQL

if (not exists(select top 1 1 from Table where StaffID = @StaffID))
begin
	insert into Table (Field1, Field2, Field3)
	values (@Param1, @Param2, @Param3)
end

Use or adapt either of these methods to suit your need but you should certainly consider wrapping everything into a stored procedure and call that rather thna constructing a sql string in code.

how to check if staffid exist before saving

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