关于主从表的问题（求帮助）
public partial class WebForm2 : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
{
string SQL = "select c.*,d.fName AS fContractType from tContractGoods a,tContract c,(select * from tContractType) d where a.fID=c.fID and c.fContractType = d.fType";
GridView1.DataSource = Binding(SQL);
GridView1.DataKeyNames = new string[] { "c.fID" };
GridView1.DataBind();
}
}
protected void GridView1_SelectedIndexChanged(object sender, EventArgs e)
{
string OrderID = Convert.ToString(GridView1.SelectedValue);
string SQL = "select a.*,c.* from tContractGoods a ,tContract c where a.fGoodsType=2 and a.fID='" + OrderID + "'";
GridView2.DataSource = Binding(SQL);
GridView2.DataBind();
}
protected void GridView2_SelectedIndexChanged(object sender, EventArgs e)
{
}
/**/
/// <summary>
/// 执行SQL语句返回一个数据表
/// </summary>
/// <param name="SQL">所要执行的SQL语句</param>
/// <returns>DataTable</returns>
protected DataTable Binding(string SQL)
{
SqlConnection myConn = new SqlConnection(ConfigurationManager.ConnectionStrings["AppConnectionString1"].ConnectionString);
DataTable dt = new DataTable();
SqlDataAdapter myAdapter = new SqlDataAdapter(SQL, myConn);
myAdapter.Fill(dt);
return dt;
}
出现如下问题；
用户代码未处理 System.NullReferenceException
Message="未将对象引用设置到对象的实例。"
Source="hager"
StackTrace:
在 hager.WebForm2.Binding(String SQL) 位置 C:\Documents and Settings\develop\My Documents\Visual Studio 2008\Projects\hager\hager\WebForm2.aspx.cs:行号 47
在 hager.WebForm2.Page_Load(Object sender, EventArgs e) 位置 C:\Documents and Settings\develop\My Documents\Visual Studio 2008\Projects\hager\hager\WebForm2.aspx.cs:行号 21
在 System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e)
在 System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e)
在 System.Web.UI.Control.OnLoad(EventArgs e)
在 System.Web.UI.Control.LoadRecursive()
在 System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
InnerException:
请问是什么问题该如何解决？
[解决办法]
给分啊，。呵呵
