C# 将datatable绑定到自定义GridView控件会生成空引用异常
将datatable绑定到自定义gridview控件时遇到问题。当我将数据绑定到控件时,遇到的问题是nullreference异常 当数据源是由SqlDataAdapter填充的datatable时,gridview绑定没有问题。下面是对我来说很有用的代码:C# 将datatable绑定到自定义GridView控件会生成空引用异常,c#,asp.net,gridview,datatable,C#,Asp.net,Gridview,Datatable,将datatable绑定到自定义gridview控件时遇到问题。当我将数据绑定到控件时,遇到的问题是nullreference异常 当数据源是由SqlDataAdapter填充的datatable时,gridview绑定没有问题。下面是对我来说很有用的代码: public override void Load(DateTime startDate, DateTime endDate) { using (DataTable dt = new DataTable())
public override void Load(DateTime startDate, DateTime endDate)
{
using (DataTable dt = new DataTable())
{
using (dbCheckpointWarehouseDataContext thisDataContext = new dbCheckpointWarehouseDataContext())
{
var qryItemCount = [LINQ QUERY THAT WORKS FINE.]
using (SqlCommand cmd = thisDataContext.GetCommand(qryItemCount) as SqlCommand)
{
using (SqlDataAdapter adapter = new SqlDataAdapter(cmd))
{
adapter.Fill(dt);
}
if (dt.Rows.Count > 0)
{
CustomGridView cgvResults = new CustomGridView();
cgvResults.AddBoundField("DistrictManagerName", "District Manager", "");
cgvResults.AddBoundField("newMetric", "newMetric", "");
cgvResults.DataSource = dt;
cgvResults.DataBind();
m_ReportHTMLString = Utilities.RenderHTMLStringOfControl(cgvResults);
}
}
}
}
}
如果我尝试用强类型datatable加载同一个自定义控件,则会出现null引用异常。在我将datatable绑定到stock gridview控件的地方注释掉了三行。这也行得通。我只有在使用带有自定义gridview的强类型数据表时才会遇到这个问题。异常是在DataBind方法中生成的。在调试模式下,我验证了datatable不是空的,并且在设置DataSource属性时没有异常。以下是生成空引用的代码:
public override void Load(DateTime startDate, DateTime endDate)
{
using (DataTable dt = new DataTable())
{
dt.Columns.Add("DistrictManagerName", typeof(string));
dt.Columns.Add("newMetric", typeof(Int32));
DataRow row;
using (dbCheckpointWarehouseDataContext thisDataContext = new dbCheckpointWarehouseDataContext())
{
var qryItemCount = [LINQ QUERY THAT WORKS FINE.]
.AsEnumerable()
.Select([SELECT STATEMENT THAT WORKS FINE])
foreach (var rowtrans in qryTest)
{
row = dt.NewRow();
row["DistrictManagerName"] = rowtrans.DistrictManagerName;
row["newMetric"] = Convert.ToInt32(rowtrans.newMetric);
dt.Rows.Add(row);
}
string total = dt.Compute("Sum(newMetric)", "").ToString();
row = dt.NewRow();
row["DistrictManagerName"] = "Total";
row["newMetric"] = String.Format("{0:#,0}", total);
dt.Rows.Add(row);
dt.AcceptChanges();
CustomGridView cgvResults = new CustomGridView();
cgvResults.AddBoundField("", "District Manager", "");
cgvResults.AddBoundField("", "Total", "");
cgvResults.DataSource = dt;
cgvResults.DataBind();
//GridView cgvResults = new GridView();
//cgvResults.DataSource = dt.DefaultView;
//cgvResults.DataBind();
m_ReportHTMLString = Utilities.RenderHTMLStringOfControl(cgvResults);
}
}
}
以下是自定义gridview控件的代码:
public CustomGridView() : base()
{
AutoGenerateColumns = true;
AllowPaging = true;
AllowSorting = true;
PageSize = 25;
GridLines = GridLines.Vertical;
CssClass = "gridView";
HeaderStyle.CssClass = "gridViewHeader";
RowStyle.CssClass = "gridViewRow";
AlternatingRowStyle.CssClass = "gridViewAlternatingRow";
PagerStyle.CssClass = "gridViewPager";
CellPadding = 3;
}
public void AddBoundField(string dataField, string headerText, string sortExpression)
{
BoundField bf = new BoundField();
if (dataField != "")
{
bf.DataField = dataField;
}
if (headerText != "")
{
bf.HeaderText = headerText;
}
if (sortExpression != "")
{
bf.SortExpression = sortExpression;
}
Columns.Add(bf);
}
感谢您提供的任何帮助。我找到了解决方案。我更改了设置:
AllowPaging = true
到
我的自定义控件现在可以正常工作了
我希望有人能够解释为什么此设置会在强类型数据集上导致NullReference异常。作为旁白,没有必要对DataTable使用using语句,因为它只是在dataset designer上实现了IDisposable的拖放功能。这同样适用于数据集。谢谢你的建议。那是我VBA时代的一个顽固分子。
AllowPaging = false