Update Gridview using OnClick Event
I'm developing a basic web form that allows users to search certain columns in a database and display those records in a GridView. I have several TextBox controls that allow users to search for a name, id, etc. I am using LinqToSql for my data access layer. It's your basic search form.
The trouble comes with the GridView I am attempting to use display the data. I have the query itself in the OnClick event method of a Button control.
protected void SearchSpecific_Click(object sender, EventArgs e)
{
MyDataContext dbContext = new MyDataContext();
var results = from row in dbContext.MyTable
select row;
if(TextBoxIsValid(IDNumber))
results = results.Where(m => m.ID == Int32.Parse(IDNumber.Text));
if (validationFlag)
{
// this part doesn't seem right
SearchResultDataset.DataSource = results;
SearchResultDataset.DataBind();
}
}
Here's the gridview, though it's nothing special:
<asp:GridView ID="SearchResultDataset" runat="server"
AlternatingRowStyle-CssClass="alt"
CssClass="search_results"
GridLines="None"
AutoGenerateColumns="true"></asp:GridView>
Everything runs smoothly until I get to the DataBind() method and a NullReferenceException was thrown. Holy exceptions, Batman!
The debugger tells me that results has the correct values, but I have a feeling it has to do with binding datasources on postback. I feel like I'm missed something... Any suggestions? I can provide a stack trace if necessary.
EDIT:
There's a much larger problem at hand. I've tried adding both a LinqDataSource and an ObjectDataSource control to my page and both throw a NullReferenceException. I constructed both using the GUI and they look perfect.
After this I then assigned a DataSource in the Page_Load method:
try开发者_运维问答
{
MyDataContext dbc = new MyDataContext();
SearchResultDataset.DataSource = dbc.MyTable;
SearchResultDataset.DataBind();
}
catch (Exception ex)
{
errText.InnerHtml = ex.ToString();
}
Came up with this exception:
System.Reflection.TargetInvocationException: Property accessor 'IsPostBack' on object 'MySite.MySite' threw the following exception:'Object reference not set to an instance of an object.' ---> System.NullReferenceException: Object reference not set to an instance of an object.
at System.Web.UI.UserControl.get_IsPostBack()
The exception is definitely being thrown in the DataBind() method. This raises the question WTF is going on? I can't seem to be able to bind a linqtosql source to my GridView. I can't seem to find the page, but I read somewhere that GridView has difficulty binding to anything that isn't a DataSet object.
UPDATE
Used SqlDataSource control to access database.
You problem appears to be that you are trying to bind your dataview to an anonymous type. As MSDN says:
Creating a DataView from a query that returns anonymous types is not supported.
Solution: use the .ToList() function to cast that var into a datatype that the dataview understands and can work with.
Like this:
SearchResultDataset.DataSource = results.ToList();
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