How to insert default value for a column in Parameterized insert SQL query

Try this

Html Code

   <asp:TextBox ID="txtInsert" runat="server"></asp:TextBox>
        <asp:Button ID="btnInsert" runat="server" Text="Insert"  OnClick ="InsertVal"/>

Code

 protected void InsertVal(object sender, EventArgs e)
    {
        string value = string.Empty;
        if (!string.IsNullOrEmpty(this.txtInsert.Text.Trim()))
        {
            value = this.txtInsert.Text.Trim();
        }
        else
        {
            value = "Default"; /* You can assign here your default value of database. */
        }
        SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["conString"].ConnectionString);
        SqlCommand cmd = new SqlCommand("INSERT INTO Table_InsertQuery VALUES (@Value)", con);
        cmd.Parameters.AddWithValue("@Value", value);
        con.Open();
        cmd.ExecuteNonQuery();
        con.Close();
    }