从List集合c＃/ asp.net填充Dropdownlist

Question

I have a class named memberdetails and memberdb which are part of my class library. I am using asp.net C# with MSSQL as the back end

My memberdetails class

     public int MemID
     {
        get { return memID; }      
     }

     public string FirstName
    {
        get { return firstName; }
        set { firstName = value; }
    }

     public MemberDetails(int memID, string firstName)
        {
        this.memID = memID;
        this.firstName = firstName;
        }

memberdb class

public List<MemberDetails> MemberResult(int memid)
    {  
        using (SqlConnection con = new SqlConnection(connectionString))         
        using (SqlCommand cmd = con.CreateCommand())
        {
            List<MemberDetails> memberdetails = new List<MemberDetails>();
            MemberDetails member;

            try
            {
                con.Open();
                cmd.CommandText = "usp_Member_Result";
                cmd.CommandType = CommandType.StoredProcedure;
                cmd.Parameters.AddWithValue("@memgen", memid);

                using (SqlDataReader reader = cmd.ExecuteReader())
                {
                    while (reader.Read())
                    {
                        member = new MemberDetails((int)reader["memid"],  (string)reader["firstname"]);
                        memberdetails.Add(member);

                    }
                    reader.Close();
                    return memberdetails;                          
                 }
            }
            catch (SqlException err)
            {
                throw new ApplicationException("Data error.", err);
            }
            finally
            {            
                if (con != null)
                    con.Close();
            }
        }
    }

After I compile those classes into a DLL and then add it as a reference to my project I am trying to bind my DropDownlist to retrieve those values. In the codebehind page I am getting a value from the gridview putting it into a variable "memgen" sending that to my method and then returning the results. When I debug my application I see the values are returned however they are not binded to the DropDownList.

CodeBehind Page

 member.MemberResult(memgen);
   // MemberDetails details = new MemberDetails();

    ddlFamilyMembers.DataTextField = "Text";
    ddlFamilyMembers.DataValueField = "Value"; 
  //  ddlFamilyMembers.DataSource = memberdetails; << "This does not exist in the current context"
    ddlFamilyMembers.DataBind();

Answer 1

Your code-behind needs to change to be something like this:

List<MemberDetails> details = member.MemberResult(memgen); 

ddlFamilyMembers.DataTextField = "FirstName"; 
ddlFamilyMembers.DataValueField = "MemID";  
ddlFamilyMembers.DataSource = details;
ddlFamilyMembers.DataBind(); 

The specific changes:

1. Capture the result of MemberResult
2. Use the correct field names for DataTextField and DataValueField
3. Set the DataSource property

Answer 2

I think the problem is that you forgot to add the datasource of the dropdownlist.

You can do as shown below :

var ddlvals = member.MemberResult(memgen); 

ddlFamilyMembers.DataTextField = "FirstName"; 
ddlFamilyMembers.DataValueField = "MemID";  
ddlFamilyMembers.DataSource = ddlvals;
ddlFamilyMembers.DataBind();

Without binding that won't work. I hope this helps your issue.

Answer 3

List<MemberDetails> details = member.MemberResult(memgen); 

ddlFamilyMembers.DataTextField = "FirstName"; 
ddlFamilyMembers.DataValueField = "MemID";  
ddlFamilyMembers.DataSource = details;
ddlFamilyMembers.DataBind();