DataGridView data retrieval confusion

I'm trying to retrieve data from database after clicking view button from windows form, but every time I click on view button the same data in database copied in multiple rows in DataGridView control, instead of retrieving the same data from starting in the DataGridView every time I click on view button.

     //For view button 
        private void button2_Click(object sender, EventArgs e)
        {
                Bi开发者_JAVA技巧ndingSource bindingSource = new BindingSource();
                bindingSource.DataSource = businesslayer.View("Select * from itemmaster"); //passed to business access layer class
                dataGridView1.DataSource = bindingSource;

        } 


//Method in DataAccessLayer class
 public DataTable View(String query)
        {
            //Initialize a connection object
            OpenConn();

            //Initalize a command object with passing string value
            command = new SqlCommand(query, connection);
            SqlDataAdapter da = new SqlDataAdapter();
            da.SelectCommand = command;

            //Fill dataset with a table
            da.Fill(dataset, thisTable);
            return dataset.Tables[thisTable];
        }

Could anyone please tell me how can I solve this problem

BindingSource bindingSource = new BindingSource(); 
dataGridView1.Items.Clear();
bindingSource.DataSource = businesslayer.View("Select * from itemmaster"); //passed to business access layer class 
dataGridView1.DataSource = bindingSource;

Try clearing your gridview before binding it to your datasource.