WebGrid provides feature to do binding after PostBack, which can be called Late Binding.

In this topic, you will learn the basic thing on how to implement Late Binding.

To Bind WebGrid after PostBack

Drag Server Button to your WebForm.

On ButtonClick event handler, add the following code:

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private void Button1_Click(object sender, System.EventArgs e)
{
      CurrentCountry = DropDownList1.SelectedValue;
      CurrentProfile = RadioButtonList1.SelectedValue;
      WebGrid1.ClearCachedDataSource();
      WebGrid1.RebindDataSource();
      WebGrid1.Visible = true;
}

Double click on the WebForm to write Page_Load codes.

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private void Page_Load(object sender, System.EventArgs e)
{
        // Put user code to initialize the page here
        if (!IsPostBack) 
        {
                OleDbDataAdapter da = new OleDbDataAdapter("select * from employees", oleDbConnection1);
                DataTable dt = new DataTable();
                da.Fill(dt);
                DropDownList2.DataSource = dt;
                DropDownList2.DataTextField = "FirstName";
                DropDownList2.DataValueField = "EmployeeID";
                DropDownList2.DataBind();
        } 
        else 
        {
                if (WebGrid1.FlyPostBackAction == PostBackAction.RefreshData) 
                {
                        // simulate button click event when refresh icon is clicked
                        Button1_Click(null, null);
                }
        }
}

Add the following code under the namespace:

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string[] Profile1_Root = {"CustomerID", "ContactTitle", "ContactName", "Country"};
string[] Profile2_Root = {"CustomerID", "Address", "CompanyName", "Phone"};

string[] Profile1_Child = {"OrderID", "OrderDate", "Freight"};
string[] Profile2_Child = {"OrderID", "EmployeeID", "RequiredDate"};

string CurrentProfile = null;
string CurrentCountry = null;

private DataSet GetCustomers(string Country, string Profile) 
{
        if (Country == null)
        return null;

        OleDbDataAdapter da = new OleDbDataAdapter("select * from customers where country='" + Country + "'", oleDbConnection1);
        OleDbDataAdapter da2 = new OleDbDataAdapter("select o.* from orders o inner join customers c on o.customerid=c.customerid where c.country='" + Country + "'", oleDbConnection1);

        DataSet ds = new DataSet();
        DataTable dt1 = new DataTable("Customers");
        DataTable dt2 = new DataTable("Orders");

        da.Fill(dt1);
        da2.Fill(dt2);

        ds.Tables.Add(dt1);
        ds.Tables.Add(dt2);

        ds.Relations.Add(ds.Tables["Customers"].Columns["CustomerID"], ds.Tables["Orders"].Columns["CustomerID"]);

        CurrentProfile = Profile;
        return ds;
}

private void CreateStructure()
{
        string[] UseProfileRoot = null;
        string[] UseProfileChild = null;

        if (CurrentProfile == "Profile1") 
        {
                UseProfileRoot = Profile1_Root;
                UseProfileChild = Profile1_Child;
        } 
        else 
        {
                UseProfileRoot = Profile2_Root;
                UseProfileChild = Profile2_Child;
        }

        WebGrid1.RootTable.Columns.Clear();
        WebGrid1.RootTable.ChildTables.Clear();
        WebGrid1.LayoutSettings.Hierarchical = true;

        WebGrid1.RootTable.DataMember = "Customers";
        WebGrid1.RootTable.DataKeyField = "CustomerID";
        foreach(string col in UseProfileRoot) 
        {
                WebGrid1.RootTable.Columns.Add(new WebGridColumn(col, col, col));
        }

        WebGridTable childTable = new WebGridTable();
        childTable.DataMember = "Orders";
        childTable.DataKeyField = "OrderID";
        foreach(string col in UseProfileChild) 
        {
                childTable.Columns.Add(new WebGridColumn(col, col, col));
        }

        WebGrid1.RootTable.ChildTables.Add(childTable);
}

private void FormatGrid() 
{
        foreach (WebGridColumn col in WebGrid1.RootTable.Columns) 
        {
                if (col.DataMember == "CustomerID")
                        col.CellStyle.HorizontalAlign = HorizontalAlign.Right;
        }

        foreach (WebGridColumn col in WebGrid1.GetTableByName("Orders").Columns) 
        {
                if (col.DataMember == "OrderDate" || col.DataMember == "RequiredDate")
                {
                        col.DataFormatString = "d";
                } 
                else 
                {
                        col.CellStyle.HorizontalAlign = HorizontalAlign.Right;
                }
        }

        WebGrid1.LayoutSettings.AllowSorting = Sorting.Yes;
}

Double click the WebGrid and add the following code under InitializeDataSource event handler.

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e.DataSource = GetCustomers(CurrentCountry, CurrentProfile);

Then, it will automatically retrieve its structure by using RetrieveStructure() method in PrepareDataBinding event handler.

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if (IsPostBack) { if (!WebGrid1.IsFlyPostBack) { CreateStructure(); } FormatGrid(); }

Add the following codes under InitializeTable event handler.

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private void WebGrid1_InitializeTable(object sender, ISNet.WebUI.WebGrid.TableEventArgs e)
{
        if (IsPostBack && !WebGrid1.IsFlyPostBack && e.Table.IsRootTable) 
        {
                if (CheckBox1.Checked) 
                {
                        // get customers rows where order's employeeid = selected value
                        OleDbDataAdapter da = new OleDbDataAdapter("select distinct customerid from orders where employeeid=" + DropDownList2.SelectedValue, oleDbConnection1);
                        DataTable dt = new DataTable();
                        da.Fill(dt);

                        foreach(WebGridRow row in WebGrid1.RootTable.Rows) 
                        {
                                foreach(DataRow dr in dt.Rows) 
                                {
                                        if (row.Cells.GetNamedItem("CustomerID").Text == dr["CustomerID"].ToString())
                                                row.ExpandChildRow();
                                }
                        }
                }
        }
}

Compile and run the WebForm.

Intersoft WebGrid Documentation
How-to: Bind WebGrid after PostBack (Late Binding)
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To Bind WebGrid after PostBack

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