我创建了一个BCS服务，并从BCS内容类型创建了一个外部列表。
然后我尝试将一个SPGridView控件添加到webpart。我在调用SPGridview的{{1}}方法后立即收到异常，代码如下：
DataBind()}
namespace BCSService.CustomWebPart
{
[ToolboxItemAttribute(false)]
public class CustomWebPart : WebPart
{
// Visual Studio might automatically update this path when you change the Visual Web Part project item.
private const string _ascxPath = @"~/_CONTROLTEMPLATES/BCSShims/CustomWorkEstimateWebPart/CustomWorkEstimateWebPartUserControl.ascx";
private SPGridView gv;
private SPDataSource spdata;
private SPSite site;
private SPWeb web;
private SPList we_list;
protected override void CreateChildControls()
{
base.CreateChildControls();
Control control = Page.LoadControl(_ascxPath);
Controls.Add(control);
this.site = SPContext.Current.Site;
this.web = this.site.OpenWeb();
this.we_list = this.web.Lists["BCSList"];
this.spdata = new SPDataSource();
Controls.Add(this.spdata);
this.gv = new SPGridView();
this.gv.AutoGenerateColumns = false;
Controls.Add(this.gv);
}
protected void BindColumns()
{
this.spdata.DataSourceMode = SPDataSourceMode.List;
this.spdata.List = this.we_list;
this.spdata.UseInternalName = true;
this.spdata.DataBind();
this.gv.AllowSorting = false;
this.gv.PageSize = 200;
this.gv.DataSource = this.spdata;
Dictionary<string, string> listFields = new Dictionary<string, string>();
listFields.Add("CompanyName", "Company Name");
listFields.Add("ContactDetails", "Contact Details");
listFields.Add("ProjectDescription", "Description");
foreach (var row in listFields)
{
SPBoundField boundField = new SPBoundField();
boundField.HeaderText = row.Value;
boundField.DataField = row.Key;
this.gv.Columns.Add(boundField);
}
}
protected override void RenderContents(HtmlTextWriter writer)
{
if (!Page.IsPostBack)
{
this.BindColumns();
this.gv.DataBind();
}
this.gv.RenderControl(writer);
}
}
方法抛出以下异常：
DataBind()我已验证Object reference not set to an instance of an object.
at Microsoft.SharePoint.WebControls.SPDataSourceViewResultItem.System.ComponentModel.ICustomTypeDescriptor.GetProperties()
at System.ComponentModel.TypeDescriptor.MergedTypeDescriptor.System.ComponentModel.ICustomTypeDescriptor.GetProperties()
at System.ComponentModel.TypeDescriptor.GetPropertiesImpl(Object component, Attribute[] attributes, Boolean noCustomTypeDesc, Boolean noAttributes)
at System.ComponentModel.TypeDescriptor.GetProperties(Object component)
at Microsoft.SharePoint.WebControls.SPBoundField.DataBindingEventHandler(Object sender, EventArgs e)
at System.Web.UI.Control.OnDataBinding(EventArgs e)
at System.Web.UI.Control.DataBind(Boolean raiseOnDataBinding)
at System.Web.UI.Control.DataBindChildren()
at System.Web.UI.Control.DataBind(Boolean raiseOnDataBinding)
at System.Web.UI.Control.DataBindChildren()
at System.Web.UI.Control.DataBind(Boolean raiseOnDataBinding)
at System.Web.UI.WebControls.GridView.CreateRow(Int32 rowIndex, Int32 dataSourceIndex, DataControlRowType rowType, DataControlRowState rowState, Boolean dataBind, Object dataItem, DataControlField[] fields, TableRowCollection rows, PagedDataSource pagedDataSource)
at System.Web.UI.WebControls.GridView.CreateChildControls(IEnumerable dataSource, Boolean dataBinding)
at Microsoft.SharePoint.WebControls.SPGridView.CreateChildControls(IEnumerable dataSource, Boolean dataBinding)
at System.Web.UI.WebControls.CompositeDataBoundControl.PerformDataBinding(IEnumerable data)
at System.Web.UI.WebControls.GridView.PerformDataBinding(IEnumerable data)
at System.Web.UI.WebControls.DataBoundControl.OnDataSourceViewSelectCallback(IEnumerable data)
at System.Web.UI.WebControls.DataBoundControl.PerformSelect()
at BCSService.CustomWebPart.CustomWorkEstimateWebPart.RenderContents(HtmlTextWriter writer)
不为空（在Visual Studio调试器的this.we_list标签中，我可以看到locals设置为99，尽管this.we_list.Items.Count设置为0 。）
此外，所有这些似乎都可以对付非外部列表，但我在this.we_list.ItemCount或SPGridView中不支持外部列表的文档中看不到任何内容，并且该例外没有提及外部列表不受支持。有没有人遇到过这个问题？
答案 0 :(得分：0)
这似乎是一个可能的Sharepoint Server 2010错误（我使用的是Sharepoint Server 2010企业版）。最后，我通过向我的BCS服务实体添加to_datatable（）转换方法解决了这个问题，该方法只使用statis ReadList（）方法，收集其输出，并将数据插入到DataTable对象中。