C# DataGridView数据检索混乱

我试图在从windows窗体单击“查看”按钮后从数据库检索数据，但每次单击“查看”按钮时，数据库中的相同数据都会复制到DataGridView控件的多行中，而不是每次单击“查看”按钮时从DataGridView中开始检索相同的数据

     //For view button 
        private void button2_Click(object sender, EventArgs e)
        {
                BindingSource 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];
        }

谁能告诉我怎么解决这个问题

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

---

在将gridview绑定到数据源之前，请尝试清除它。

但是，我在DataGridView类中没有找到任何Items属性，那么它怎么可能是真的呢？它应该是dataGridView1.Items.Clear。