如何通过弹出窗口获取警报消息？

Question

在这里，当我选择相同的日期和相同的批次时，应该弹出警告消息。 我尝试了try catch方法，但是没有用，告诉我哪里出了问题。

到目前为止我的代码

using (SqlConnection con2 = new SqlConnection(ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString))
        {
            var fromdate = DateTime.Parse(txtfromdate.Text);
            var todate = DateTime.Parse(txttodate.Text);
            var datedif1 = (todate - fromdate).Days;

            var sqlInsert = new SqlCommand("INSERT INTO datelist ([datedif],[batch],[daywk],[semester],[weekbatch],[subject],[facultyname],[facultyid],[WeekMonth])  SELECT * from (SELECT @datedif as datedif, @batch as batch,@daywk as daywk,@semester as semster,@weekbatch as weekbatch,@subject as subject,@facultyname as facultyname,@facultyid as facultyid,@weekMonth as weekMonth) AS temp WHERE NOT EXISTS (SELECT datedif,batch from datelist where batch=@batch and datedif=@datedif)", con2);

            var sqlParamater = sqlInsert.Parameters.Add("@datedif", SqlDbType.Date);
            var sqlParameter1 = sqlInsert.Parameters.Add("@batch", SqlDbType.NVarChar);
            var sqlParameter2 = sqlInsert.Parameters.Add("@daywk", SqlDbType.NVarChar);
            var sqlParameter3 = sqlInsert.Parameters.Add("@semester", SqlDbType.NVarChar);
            var sqlParameter4 = sqlInsert.Parameters.Add("@weekbatch", SqlDbType.NVarChar);
            var sqlParameter5 = sqlInsert.Parameters.Add("@subject", SqlDbType.NVarChar);
            var sqlParameter6 = sqlInsert.Parameters.Add("@facultyname", SqlDbType.NVarChar);
            var sqlParameter7 = sqlInsert.Parameters.Add("@facultyid", SqlDbType.NVarChar);
            var sqlParameter8 = sqlInsert.Parameters.Add("@WeekMonth", SqlDbType.NVarChar);

            con2.Open();
           try
            {
                for (var i = 0; i <= datedif1; i++)
                {
                    var consecutiveDate = fromdate.AddDays(i);

                    sqlParamater.Value  = consecutiveDate;
                    sqlParameter1.Value = batch1;
                    sqlParameter2.Value = dayweek;
                    sqlParameter3.Value = semester;
                    sqlParameter4.Value = weekbatch;
                    sqlParameter5.Value = subject;
                    sqlParameter6.Value = faculty;
                    sqlParameter7.Value = facultyid;
                    sqlParameter8.Value = weekmonth;

                    int s = sqlInsert.ExecuteNonQuery();
                }

            }

            catch
            {
                Response.Write("<script>alert('Already date is selected.Select another date')</script>");
                con2.Close();
           }
        }
    }

Answer 1

1-请先检查您是否要在catch块中放入调试器。
2-将调试器也放在页面加载上，以检查它何时发生。

您可以使用RegisterStartupScript（）方法
在服务器端

 catch
        {
string msg="Already date is selected.Select another date";
ScriptManager.RegisterStartupScript(this, GetType(), "myFunction",      "myFunction('"+msg+"');", true); 
 }

在客户端

<script>
        function myFunction(a) {

            alert(a);        
        }
    </script>

另外最好进行一些存储过程。