Faster way to load drop down list - asp.net

Question

So I am having a problem loading a drop down list in an asp.net web forms site. I am pulling the records from a SQL Server database. I am binding the results to a drop down list.
My problems stems from the fact that I am retrieving 21500 plus rows and it is causing a long delay to the point where the browser throws a message asking if I want to stop a long executing script. If I wait long enough, ~2 minutes it will come back but still runs very slow taking a long time scroll down through the list.
Here is the VB code for the SQL call:
Private Function GetCorInfo(field As String, tblname As String, Optional whereClause As String = "") As DataTable
Dim sqlCmdTxt As String = "Select " & field & " From " & tblname
Using conn As New SqlConnection(corConnection)
Try
conn.Open()
Catch ex As Exception
Master.message = "Unable to open SQL DB connection\nError: SQL101\nPlease contact the Help Desk for support.\n" & HttpUtility.JavaScriptStringEncode(ex.Message)
jsa.alertmessage(passedPage, Master.message)
End Try
Using sqlCmd As New SqlCommand
'Check for where clause
If whereClause <> "" Then
sqlCmdTxt = sqlCmdTxt & whereClause
If whereClause.Substring(7, 6) = "cornum" Then
sqlCmd.Parameters.AddWithValue("#cornum", ddl2.SelectedItem.Text)
End If
End If
If field = "cornum" Then
sqlCmdTxt = sqlCmdTxt & " Order By " & field & " Desc"
End If
sqlCmd.CommandText = sqlCmdTxt
sqlCmd.Connection = conn
Using sqlDT As New DataTable()
Using sqlDA As New SqlDataAdapter(sqlCmd)
Try
sqlDA.Fill(sqlDT)
Return sqlDT
Catch ex As Exception
conn.Close()
Master.message = "Unable to load list.\nError: SQL104\n" & HttpUtility.JavaScriptStringEncode(ex.Message)
jsa.alertmessage(passedPage, Master.message)
Return Nothing
End Try
End Using
End Using
End Using
End Using
End Function
Then when the data table is returned I am binding it to the drop down list using this code:
If Not IsNothing(dt) Then
'Set ddl
With ddl
'Turn on ddl
.Visible = True
'Set Data Source
.DataSource = dt
'Set Text Field
.DataTextField = field1
'Set Value Field
.DataValueField = field1
'Set variable to field value
'Bind Data
.DataBind()
'Assign Variable
field = ddl.SelectedItem.Text
'Check for ddl match
If whereClause <> "" AndAlso ddl1.SelectedIndex = 3 AndAlso ddl.ID = "ddl3" Then
.Items.FindByValue(field).Selected = True
ElseIf whereClause <> "" AndAlso ddl1.SelectedIndex = 3 AndAlso ddl.ID = "ddl4" Then
.Items.Insert(0, New ListItem("Select", "0"))
Else
'Insert first choice
.Items.Insert(0, New ListItem("Select", "0"))
End If
'Set to index 0
.SelectedIndex = 0
End With
Return 1
Else
Return -1
End If
Both sets of codes are run in functions.
How can I speed this up? I have looked at using Session and View State but the number of returned records would cause a bigger slow down if I do that.
Does anyone have any ideas?
Thanks in advance for the help.

Answer 1

So this what i finally did.
Placed a text box for the user to type in the first few char's of a new customer name. Then taking that I build a SQL query that only returns records that match the chars entered.
Much faster and only have at max 35 records...