需要帮助将参数传递给ExecuteScalar [英] Need a help to pass parameter into ExecuteScalar

问题描述

Hello all



我收到一条错误消息：对象引用未设置为对象的实例。行旁边：有人可以帮我修复此错误

  var  orderExists =（ Int32 ）ChkavailbleJobCMD.ExecuteScalar（）>   0 ; 

  protected   void  LinkBut​​ton4_Click（ object  sender，EventArgs e）
 {
 JobsMView.ActiveViewIndex =  2 ; 
 
 使用（ var  UsOrderCon =  new  SqlConnection（cs））
 {
 UsOrderCon.Open（）; 
 
  string  chksBervJobsSt =  选择JobNum，Jobtitle，Dept，VacCountry，Employer from Employer = @ Emp; 
 
 SqlCommand ChkavailbleJobCMD =  new  SqlCommand（chksBervJobsSt，UsOrderCon）; 
 
 ChkavailbleJobCMD.Parameters.AddWithValue（  @Emp，  Berava）; 
 
  var  orderExists =（ Int32 ）ChkavailbleJobCMD.ExecuteScalar（）>   0 ; 
 
 
  if （orderExists）
 {
 jobsAvaPan.Visible = 真; 
 
 SqlDataAdapter BervJonavaADPA =  new  SqlDataAdapter（  SELECT JobNum，Jobtitle，Dept，VacCountry，Employer FROM jobs WHERE Employer = @Emp，cs）; 
 
 BervJonavaADPA.SelectCommand.Parameters.AddWithValue（  @Emp，< span class =code-string>  Berava）; 
 
 DataSet BervJonavaDST =  new  DataSet（）; 
 BervJonavaADPA.Fill（BervJonavaDST）; 
 GridView1.DataSource = BervJonavaDST.Tables [ 0 ]; 
 GridView1.DataBind（）; 
 
} 
  else  
 {
 NoJobAvPan.Visible = 真; 
 NoJobLbl.Text =  抱歉，我们目前没有任何工作可用; 
} 
} 
} 

解决方案

更改

 选择 JobNum，Jobtitle，Dept，VacCountry，雇主来自的工作其中雇主= @Emp 

to

 选择 count（*）来自作业其中雇主= @ EMP 

Hello all

I am getting an error message: " Object reference not set to an instance of an object. " next to line: so can someone help me to fix this error

var orderExists = (Int32)ChkavailbleJobCMD.ExecuteScalar() > 0;

protected void LinkButton4_Click(object sender, EventArgs e)
        {
            JobsMView.ActiveViewIndex = 2;

            using (var UsOrderCon = new SqlConnection(cs))
            {
                UsOrderCon.Open();

                string chksBervJobsSt = "Select JobNum, Jobtitle, Dept, VacCountry, Employer from jobs where Employer=@Emp";

                SqlCommand ChkavailbleJobCMD = new SqlCommand(chksBervJobsSt, UsOrderCon);

                ChkavailbleJobCMD.Parameters.AddWithValue("@Emp", "Berava");

                var orderExists = (Int32)ChkavailbleJobCMD.ExecuteScalar() > 0;


                if (orderExists)
                {
                    jobsAvaPan.Visible = true;

                    SqlDataAdapter BervJonavaADPA = new SqlDataAdapter("SELECT JobNum, Jobtitle, Dept, VacCountry, Employer FROM jobs WHERE Employer = @Emp ", cs);

                    BervJonavaADPA.SelectCommand.Parameters.AddWithValue("@Emp", "Berava");

                    DataSet BervJonavaDST = new DataSet();
                    BervJonavaADPA.Fill(BervJonavaDST);
                    GridView1.DataSource = BervJonavaDST.Tables[0];
                    GridView1.DataBind();

                }
                else
                {
                    NoJobAvPan.Visible = true;
                    NoJobLbl.Text = "Sorry, we don't have any job available at the moment";
                }
            }
        }

解决方案

change

Select JobNum, Jobtitle, Dept, VacCountry, Employer from jobs where Employer=@Emp

to

Select count(*) from jobs where Employer=@Emp

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