SPQuery search doesn't work with "BeginsWith" - sharepoint

Question

So, my problem is that my knowledge of CAML and Sharepoint is very poor.
Question: I need SPQuery for building query search, search text I have from textbox. I expect that my query returns me item(s) (for example, I type in textbox "Jo" and query returns me all items with surname "Johnson", or name "John", etc)
1)TextChanged works ok. I've check it, there is ok
2) SPGridView views items ok. Items from SPList I add to gridView - there are viewd by gridview.
3) But my query doesn't work. Please, help with links/advises
public class VisualWebPart1 : WebPart
{
SPSite site;
SPWeb web;
SPGridView gridView;
SPDataSource dataSource;
TextBox searchTextBox;
UpdatePanel panel;
SPList list;
SPList resultList;
string currentList;
// Visual Studio might automatically update this path when you change the Visual Web Part project item.
private const string _ascxPath = #"~/_CONTROLTEMPLATES/CRMSearchWebPart/VisualWebPart1/VisualWebPart1UserControl.ascx";
protected override void CreateChildControls()
{
gridView = new SPGridView();
searchTextBox = new TextBox();
panel = new UpdatePanel();
searchTextBox.AutoPostBack = true;
searchTextBox.Visible = true;
searchTextBox.Enabled = true;
searchTextBox.TextChanged += new EventHandler(searchTextBox_TextChanged);
gridView.Visible = true;
gridView.Enabled = true;
gridView.AutoGenerateColumns = false;
AddColumnToSPGridView("Surname", "Surname");
panel.UpdateMode = UpdatePanelUpdateMode.Conditional;
panel.ContentTemplateContainer.Controls.Add(searchTextBox);
panel.ContentTemplateContainer.Controls.Add(gridView);
Control control = Page.LoadControl(_ascxPath);
Controls.Add(control);
Controls.Add(panel);
}
protected override void Render(HtmlTextWriter writer)
{
panel.RenderControl(writer);
}
//Open WebSite with List "listName"
private void OpenWebSite(string listName)
{
site = SPContext.Current.Site;
web = site.OpenWeb();
list = web.Lists[listName];
}
//Add Column to gridView
private void AddColumnToSPGridView(string HeaderText, string Datafield)
{
SPBoundField boundField = new SPBoundField();
boundField.HeaderText = HeaderText;
boundField.DataField = Datafield;
gridView.Columns.Add(boundField);
}
//Build query for search; fieldName - Name of column of current List, searchQuery - our query
private string BuildQuery(string fieldRefName, string searchQuery)
{
string query = "";
switch (fieldRefName)
{
case "Surname":
query = "<Where><BeginsWith><FieldRef Name='Surname'/>" +
"<Value Type=Text>"+searchQuery+"</Value></BeginsWith></Where>";
break;
case "Name":
query = query = "<Where><BeginsWith><FieldRef Name='Name'/>" +
"<Value Type=Text>"+searchQuery+"</Value></BeginsWith></Where>";
break;
case "PassportNumber":
query = "<Where><BeginsWith><FieldRef Name='PassportNumber'/>" +
"<Value Type=Text>"+searchQuery+"</Value></BeginsWith></Where>";
break;
default: break;
}
return query;
}
// search in List for selected items and returns SPGridView
private void searchTextBox_TextChanged(object sender, EventArgs e)
{
dataSource = new SPDataSource();
string querySearch = searchTextBox.Text;
OpenWebSite("Surnames");
string query = BuildQuery("Surname", querySearch);
SPQuery spQuery = new SPQuery();
spQuery.ViewFields = "<FieldRef Name = 'Title'/><FieldRef Name = 'Surname'/><FieldRef Name = 'Name'/>";
spQuery.Query = query;
SPListItemCollection items = list.GetItems(query);
foreach (SPListItem item in items)
{
searchTextBox.Text += item["Surname"] + " ";
}
//resultList = web.Lists["TempSurnames"];
//resultList = AddItemsToSPList(resultList, items);
BindDataSource(dataSource, resultList);
//resultList = AddSPList("Result2", "Result list");
//resultList = AddItemsToSPList(resultList, items);
list = AddItemsToSPList(list, items);
//BindDataSource(dataSource, resultList);
BindDataSource(dataSource, list);
BindGridView(gridView, dataSource);
//var item = list.Items[3];
//var item = resultList.Items[1];
//searchTextBox.Text = item["Surname"].ToString();
//resultList.Delete();
}
//Binds datasource of existing gridView with SPDataSource
private void BindGridView(SPGridView gridview, SPDataSource datasource)
{
gridview.DataSource = datasource;
gridview.DataBind();
}
//Add SPListItem items to SPList
private SPList AddItemsToSPList(SPList spList, SPListItemCollection collection)
{
foreach (SPListItem item in collection)
{
var listItem = spList.AddItem();
listItem = item;
}
return spList;
}
//Binds existing SPDataSource to SPList
private void BindDataSource(SPDataSource spDataSource, SPList spList)
{
spDataSource.List = spList;
}
private SPList AddSPList(string listName, string listDescription)
{
OpenWebSite("Surnames");
SPListCollection collection = web.Lists;
collection.Add(listName, listDescription, SPListTemplateType.CustomGrid);
resultList = web.Lists[listName];
return resultList;
}
Update:
This part gives me an error:
SPListItemCollection items = list.GetItems(query);
foreach (SPListItem item in items)
{
searchTextBox.Text += item["Surname"] + " ";
}
System.ArgumentException: Value does not fall within the expected
range

Answer 1

You have to include the field Surname into the view fields of the query:
SPQuery query = // ...
query.ViewFields = "<FieldRef Name='Surname' />";
// ...
You can understand the view fields like the SELECT part of a SQL query.

Answer 2

Have you debugged your code to check the query string that is generated? Also, you have query = query = under the Name switch.
Also, you know that the switch is case sensitive, so ensure you enter your searchQuery option appropriately.