将外部 (BCS) 列表绑定到 Sharepoint 2010 中的 SPDataGrid

Question

我创建了 BCS 服务并从 BCS 内容类型创建了外部列表。 然后，我尝试将 SPGridView 控件添加到 Web 部件。当我调用 SPGridview 的 DataBind() 方法时，我遇到了异常，代码如下：

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);
    }
}

}

DataBind()< /code> 方法抛出以下异常：

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)

我已验证 this.we_list 不为空（在 Visual Studio 调试器的 locals 选项卡中，我可以看到 this.we_list ）。 we_list.Items.Count 设置为 99，尽管 this.we_list.ItemCount 设置为 0。）

此外，这一切似乎都适用于非外部列表，但我看到文档中没有提到 SPGridView 或 SPDataSource 不支持外部列表，并且该异常也没有提及不支持外部列表。有人遇到过这个问题吗？

Answer 1

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）。最终，我通过向 BCS 服务实体添加 to_datatable() 转换方法解决了该问题，该方法仅使用 statis ReadList() 方法，收集其输出，并将数据插入到 DataTable 对象中。