异常详细信息: System.NullReferenceException: 未将对象引用设置到对象的实例。???????

异常详细信息: System.NullReferenceException: 未将对象引用设置到对象的实例。

源错误:


行 27: {
行 28: DataRow SmallClassName =DBOperate.GetDataRow("select * from Small_Class where SmallClass_ID="+SmallClass_ID,"Small_Class","DBConnection");
行 29: return SmallClassName["SmallClass_ID"].ToString();
行 30: }
行 31: }


源文件: c:\Inetpub\wwwroot\TragramMini\WebTragMini\App_Code\Navigation.cs 行: 29

堆栈跟踪:


[NullReferenceException: 未将对象引用设置到对象的实例。]
TangramMiniWeb.Navigation.GetSmallClassName(Int32 SmallClass_ID) in c:\Inetpub\wwwroot\TragramMini\WebTragMini\App_Code\Navigation.cs:29
TangramMiniWeb.pith.Page_Load(Object sender, EventArgs e) in c:\Inetpub\wwwroot\TragramMini\WebTragMini\tan\pith.aspx.cs:132
System.Web.UI.Control.OnLoad(EventArgs e) +99
System.Web.UI.Control.LoadRecursive() +47
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1061


它的源码：


public static string GetBigClassName(int BigClass_ID)
{
DataRow BigClassName =DBOperate.GetDataRow("select * from Big_Class where BigClass_ID="+BigClass_ID,"Big_Class","DBConnection");
return BigClassName["BigClass_ID"].ToString();


}

public static string GetSmallClassName(int SmallClass_ID)
{
DataRow SmallClassName =DBOperate.GetDataRow("select * from Small_Class where SmallClass_ID="+SmallClass_ID,"Small_Class","DBConnection");
return SmallClassName["SmallClass_ID"].ToString();-------此句有问题，就是它测试不过去的？？？？？？？？？
}


用到的数据库的表为：
CREATE TABLE [dbo].[Small_Class](
[SmallClass_Id] [int] IDENTITY(1,1) NOT NULL,
[BigClass_Id] [int] NULL,
[SmallClass_Name] [nvarchar](255) COLLATE Chinese_PRC_CI_AS NULL,
[Enable] [int] NULL,
[Memo] [nvarchar](255) COLLATE Chinese_PRC_CI_AS NULL
primary key ([SmallClass_Id])
)

public static DataRow GetDataRow(string sql, string TableName, string dbname)
{

SqlConnection sqlConnection = new SqlConnection(strCon);
SqlDataAdapter sqlAdapter1 = new SqlDataAdapter(sql, sqlConnection);
DataSet product = new DataSet();
sqlAdapter1.Fill(product, TableName);
return product.Tables[0].Rows.Count == 0 ? null : product.Tables[0].Rows[0];
}