Auto Suggestion textbox - sql-server

Question

I want to have a auto suggestion textbox which will show the name of employee after typing a specific letter. The name is present in the employee table in three columns i.e firstname, middlename, lastname.
I have tried a code for this but it can show only one column of the table i.e the firstname.
How to concatenate all the three columns so that they are suggested in the textbox.
My code:
Dim strSql As String = "select P_Firstname, P_MiddleName, P_LastName from Patient_Registration"
Dim dtb As New DataTable
Using cnn As New SqlConnection(conn)
cnn.Open()
Using dad As New SqlDataAdapter(strSql, cnn)
dad.Fill(dtb)
End Using
cnn.Close()
End Using
txtsearch.AutoCompleteMode = AutoCompleteMode.SuggestAppend
txtsearch.AutoCompleteSource = AutoCompleteSource.CustomSource
If dtb.Rows.Count > 0 Then
Dim i As Integer = 0
For i = 0 To (dtb.Rows.Count - 1)
txtsearch.AutoCompleteCustomSource.Add(dtb.Rows(i)("P_FirstName"))
Next
End If

Answer 1

Use:
For i = 0 To (dtb.Rows.Count - 1)
txtsearch.AutoCompleteCustomSource.Add(dtb.Rows(i)("P_FirstName") &
dtb.Rows(i)("P_MiddleName") &
dtb.Rows(i)("P_LastName"))
Next
Instead of:
For i = 0 To (dtb.Rows.Count - 1)
txtsearch.AutoCompleteCustomSource.Add(dtb.Rows(i)("P_FirstName"))
Next

Answer 2

<asp:TextBox ID="ddlcenter" runat="server" Font-Size="10px" TabIndex="1" Width="150px"
Style="text-transform: capitalize;"
placeholder="Type Center Name/Code" autocomplete="off"></asp:TextBox>
<cc1:AutoCompleteExtender ServiceMethod="GetCenter" MinimumPrefixLength="2" CompletionInterval="100"
EnableCaching="false" CompletionSetCount="10" TargetControlID="ddlcenter" UseContextKey="true"
ID="AutoCompleteExtender1" runat="server" FirstRowSelected="false" CompletionListCssClass="completionList"
CompletionListHighlightedItemCssClass="itemHighlighted" CompletionListItemCssClass="listItem">
</cc1:AutoCompleteExtender>

Answer 3

[enter image description here][1]
[1]: https://i.stack.imgur.com/g6TR9.png
Showing above result.
enter code here
My code is :
[System.Web.Script.Services.ScriptMethod()]
[System.Web.Services.WebMethod]
public static List<string> GetCenter(string prefixText, int count)
{
using (SqlConnection conn = new SqlConnection())
{
conn.ConnectionString = ConfigurationManager.AppSettings["ConnectionString"].ToString();
using (SqlCommand cmd = new SqlCommand())
{
string cmdText = "Select centername from Center_Master WHere Active=1 and centername like '%' +#SearchText + '%'";
cmd.Parameters.AddWithValue("#SearchText", prefixText);
cmdText += " order by centername ";
cmd.CommandText = cmdText;
cmd.Connection = conn;
conn.Open();
List<string> customers = new List<string>();
using (SqlDataReader sdr = cmd.ExecuteReader())
{
while (sdr.Read())
{
customers.Add(sdr["centername"].ToString());
}
}
conn.Close();
return customers;
}
}
}