dropdownlist 空值不让提交怎么做

Question

dropdownlist  空值不让提交怎么做

Answer 1

讲清楚些 
是不是提交前要验证droplist的值不能为空

Answer 2

if(dropdownlist1.selectvalue==null)
{
response.write("不能为空");
}
else
{
//提交
}

Answer 3

<script>
function checkData()
{
if(document.getElementById("dropdownlistID").value="") return false;
else return true;
}
</script>
<input type="submit" value="提交" onclick="javascript: if(!checkData()) return false;">

Answer 4

if(dropdownlist1.selectvalue==null)
{
response.write("不能为空");
}
else
{
}

Answer 5

默认是这样的也能提交．
我想只有下面的内容才能提交．<category value="0" text="请选择">

Answer 6

if(this.ddl.selectvalue.equals("0"))
{//提交
}
else
{
  //不提交
}

Answer 7

这样好像不行哦 protected void Button1_Click(object sender, EventArgs e)
    {        if (Page.IsValid)
        {            if (ddl1.SelectedValue==null)
            {
                Response.Write("failt");
            }
            else
            {                String strConnection = ConfigurationSettings.AppSettings["ConnectionString"];//公用
                cn = new SqlConnection(strConnection);
                SqlCommand cm = new SqlCommand("classdata1", cn);
                cm.CommandType = CommandType.StoredProcedure;
                DateTime dt = DateTime.Now;
                cm.Parameters.Add(new SqlParameter("@usort", SqlDbType.VarChar, 50));
                cm.Parameters.Add(new SqlParameter("@utypename", SqlDbType.VarChar, 50));
                cm.Parameters.Add(new SqlParameter("@uwenti", SqlDbType.VarChar, 50));
                cm.Parameters.Add(new SqlParameter("@uwentilist", SqlDbType.VarChar, 50));
                cm.Parameters.Add(new SqlParameter("@ipaddress", SqlDbType.VarChar, 50));
                cm.Parameters["@usort"].Value = ddl1.SelectedItem.Text;
                cm.Parameters["@utypename"].Value = ddl2.SelectedItem.Text;
                cm.Parameters["@uwenti"].Value = dd3.SelectedItem.Value;
                cm.Parameters["@uwentilist"].Value = t1.Text;
                cm.Parameters["@ipaddress"].Value = Request.UserHostAddress;
                cm.Connection.Open();
                ;
                try
                {
                    cm.ExecuteNonQuery();                    Response.Write("<script language=javascript>alert('提交成功,请等待管理员处理');</script>");
                }
                catch (SqlException)
                {
                    //Response.Write(mydown1.Items.Count);
                    //Lbl_note.Text = "添加失败";
                    //Lbl_note.Style["color"] = "red";
                }
                cm.Connection.Close();
            }        }
    }

Answer 8

只要你的下拉菜单有东西，selectvalue肯定不空的
用selectvalue.equals()

Answer 9

if(this.DropDownList1.SelectedValue.ToString()==null)