GetFieldByDisplayName error in CAML query

Question

I'm developing a web-part for SharePoint 2010.

I've to sort a SPGridView so I use SortExpression.

I execute a CAML query in this way and then I bind data to SPGridView:

            SPQuery query = new SPQuery();
            query.RowLimit = 30;
            query.Query = "<OrderBy><FieldRef Name=\"" + sortColumn + "\" Ascending=\"" + sortDir + "\" /></OrderBy>";
            query.ViewFields = "<FieldRef Name=\"Title\" />" +
                               "<FieldRef Name=\"DocIcon\" />" +
                               "<FieldRef Name=\"Ragione_x0020_Sociale\" />" +
                               "<FieldRef Name=\"Tipo_x0020_Protocollo\" />" +
                               "<FieldRef Name=\"Data_x0020_Protocollo\" />" +
                               "<FieldRef Name=\"Formato_x0020_Documento\" />" +
                               "<FieldRef Name=\"Utilizzatore_x0020_Interno\" />" +
                               "<FieldRef Name=\"Note\" />" +
                               "<FieldRef Name=\"Descrizione\" />";

            //query.QueryThrottleMode = SPQueryThrottleOption.Override;
            string listName = "Protocolli";
            SPList list = SPContext.Current.Web.Lists[listName];
            //list.EnableThrottling = false;

            if (!string.IsNullOrEmpty(pagingInfo))
            {
                SPListItemCollectionPosition position = new SPListItemCollectionPosition(pagingInfo);
                query.ListItemCollectionPosition = position;
            }

            SPListItemCollection collection = list.GetItems(query);
            grdProtocolli.DataSource = collection.GetDataTable();

            grdProtocolli.PagerTemplate = null;  // Must be called after Controls.Add(oGrid)
            grdProtocolli.DataBind();

sortColumn is:

if (ViewState["SortExpression"] == null)
            {
                sortColumn = "Data_x0020_Protocollo";
            }
            else
            {
                sortColumn = ViewState["SortExpression"].ToString();
            }

Data_x0020_Protocollo is a field that currently exists.

Now, trying to execute my web-part I receive this error:

0x0AB0 SharePoint Foundation Runtime tkau Unexpected System.ArgumentException: Impossibile trovare un campo con il nome "Data_x0020_Protocollo". at Microsoft.SharePoint.SPFieldCollection.GetFieldByDisplayName(String strDisplayName, Boolean bThrowException)

"Impossibile trovare un campo con il nome..." is translated like "Impossible to find a field with name"

If I use the display name Data Protocollo I don't get the error anymore (and I can see the GridView), but sorting is not working.

Any suggestions?

Answer 1

Couple of things.

1. You need to handle OnSorting event and manually sort the DataTable. Then put the datatable back into ViewState
2. You should use DisplayName

Pseudo Code

protected void grdProtocolli_Sorting(object sender, GridViewSortEventArgs e)  
{  
    string sortingDirection = //LOGIC TO SET DIRECTION

    //direction is the public property
    if (direction == SortDirection.Ascending)  
    {  
        direction = SortDirection.Descending;  
        sortingDirection = "Desc";
    }  
    else  
    {  
        direction = SortDirection.Ascending;  
        sortingDirection = "Asc";         
    }  

    DataView sortedView = //Get DataView from DataTable.. You might need to read it from either ViewState or directly from the Grid View Control
    sortedView.Sort = e.SortExpression + " " + sortingDirection;  
    Session["Next"] = sortedView;  
    grdProtocolli.DataSource = sortedView;  
    grdProtocolli.DataBind();  
}