Auto complete textbox from mdf (master SQL Server database file) - sql-server

Question

I'm trying to use an autocomplete textbox, fed from a SQL Serve .mdf database file.
This is my code:
Dim cmd As New SqlCommand("Select col_name FROM college ", cn)
If cn.State = ConnectionState.Closed Then cn.Open()
Dim ds As New DataSet
Dim sqda As New SqlDataAdapter(cmd)
sqda.Fill(ds, "college")
Dim col As New AutoCompleteStringCollection
Dim i As Integer
For i = 0 To ds.Tables(0).Rows.Count - 1
col.Add(ds.Tables(0).Rows(i)("col_name").ToString())
Next
TextBox1.AutoCompleteSource = AutoCompleteSource.CustomSource
TextBox1.AutoCompleteCustomSource = col
TextBox1.AutoCompleteMode = AutoCompleteMode.Suggest
Since I am using SQL Server, the data not showing in the list.
I think its needs to use character N like
Insert data into SQL Server as:
cmd = New SqlCommand("insert into college (col_name) values (N'" & TextBox1.Text.Trim & "')", cn)

Answer 1

Keep your database objects local so you can control the closing and disposing. Using...End Using blocks handle this even if there is an error.
Always use parameters to avoid Sql injection.
In .net Char supports Unicode so strings (which are arrays of Char) also support Unicode. As long as the field in Sql Server is of type NVarChar. I don't see a problem
Private Sub SetUpAutoComplete()
Dim dt As New DataTable
Using cn As New SqlConnection("Your connection string")
Using cmd As New SqlCommand("Select col_name FROM college ", cn)
cn.Open()
dt.Load(cmd.ExecuteReader)
End Using
End Using
Dim col As New AutoCompleteStringCollection
For Each row As DataRow In dt.Rows
col.Add(row("col_name").ToString)
Next
'Just to check if we have some data
Debug.Print(col.Count.ToString)
TextBox3.AutoCompleteSource = AutoCompleteSource.CustomSource
TextBox3.AutoCompleteCustomSource = col
TextBox3.AutoCompleteMode = AutoCompleteMode.Suggest
End Sub
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
SetUpAutoComplete()
End Sub
Private Sub InsertCollege()
Using cn As New SqlConnection("Your Connection string")
Using cmd As New SqlCommand("insert into college (col_name) values (#Name)", cn)
cmd.Parameters.Add("#Name", SqlDbType.NVarChar).Value = TextBox1.Text.Trim
cn.Open()
cmd.ExecuteNonQuery()
End Using
End Using
End Sub