Dynamically Insert Data in Gridview(Rawdata) using c#

In load Event type following C# code:

 if (!this.IsPostBack)
        {
            DataTable dt = new DataTable();
            dt.Columns.AddRange(new DataColumn[4] { new DataColumn("medicin_name"), new                       DataColumn("dosage"), new DataColumn("period"), new DataColumn("dosage_type") });
            ViewState["medicindetails"] = dt;
            this.BindGrid();
        }

Create function for bind gridview:

 protected void BindGrid()
    {
        GridView1.DataSource = (DataTable)ViewState["medicindetails"];
        GridView1.DataBind();
    }

type following code in buttun click event:

 protected void Button1_Click(object sender, EventArgs e)

    {

        DataTable dt = (DataTable)ViewState["medicindetails"];

        dt.Rows.Add(m_name.Text.Trim(),ddl_dosage.SelectedItem.Text.Trim(),period.Text.Trim(),

        ddl_dosage_type.SelectedItem.Text.Trim());

        ViewState["medicindetails"] = dt;

        this.BindGrid();

        m_name.Text = string.Empty;

        ddl_dosage.SelectedIndex = 0;

        ddl_dosage_type.SelectedIndex = 0;

        period.Text = string.Empty;

        

    }

Add data in Gridview