ASP. DropDownList Findbyvalue Object reference not set to an instance of an object workaround

1, Careless put the field name in DataValueField wrong.

2. Write DataBind () behind Findbyvalue (), the following code is in the correct order:

1Bll. Student Bllstu =NewBLL.
Student (); 2 //set up a data source
3Studdl.datasource =bllstu.getstudentlist ();4 //Set display data field name
5Studdl.datatextfield ="Stuname";
6 //Set Value field name
7Studdl.datavaluefield ="Stuid";
8 //binding
9 Studdl.databind ();Ten //Set the selected value
 OneStuDDL.Items.FindByValue (Stuid). Selected =true;

3. The data source did not find the value. That should add a non-null judgment, the code is as follows:

1Bll. Student Bllstu =NewBLL.
Student (); 2  //set up a data source
3Studdl.datasource =bllstu.getstudentlist ();4  //Set display data field name
5Studdl.datatextfield ="Stuname";
6  //Set Value field name
7Studdl.datavaluefield ="Stuid";
8  //binding
9 Studdl.databind ();Ten  //Getchecked Values
 One  ObjectFindvalue=StuDDL.Items.FindByValue (stuid); A  if(findvalue!=NULL)
 -  {
 -findvalue.selected =true;
 the  }

ASP. DropDownList Findbyvalue Object reference not set to an instance of an object workaround