asp.net - 你调用的对象是空的。

Question

我下面的代码在编译时没有任何错误，但是当我打开页面时，在 Guid currentUserId = (Guid)currentUser.ProviderUserKey; 处发生错误。声明对象引用未设置为对象的实例。

foreach(DataRowView ProfileInfo in UserProfileDataSource.Select(DataSourceSelectArguments.Empty))
            {
              //Some codes where I display data from database
            }



protected void UserProfileDataSource_Selecting(object sender, SqlDataSourceSelectingEventArgs e)
    {
        MembershipUser currentUser = Membership.GetUser();

        Guid currentUserId = (Guid)currentUser.ProviderUserKey;

        e.Command.Parameters["USERID"].Value = currentUserId;
    }

这是我的 SQLDataSource

<asp:SqlDataSource ID="UserProfileDataSource" runat="server" 
            ConnectionString="<%$ ConnectionStrings:ConnectionString %>" 
            onselecting="UserProfileDataSource_Selecting" 
            ProviderName="<%$ ConnectionStrings:ConnectionString.ProviderName %>"


            SelectCommand="SELECT &quot;TITLE&quot;, &quot;FAMILYNAME&quot;, &quot;GIVENNAME&quot;, &quot;MIDDLENAME&quot;, &quot;POSITION&quot;, &quot;INSTITUTIONNAME&quot;, &quot;USERID&quot;, &quot;REGISTEREDDATE&quot; FROM &quot;MEMBERINFO&quot; WHERE (&quot;USERID&quot; = ?)">
            <SelectParameters>
                <asp:Parameter Name="USERID" Type="Object" />
            </SelectParameters>
        </asp:SqlDataSource>

厄尼

Answer 1

在尝试访问它之前，您应该检查以确保 currentUser 不为空:

if ( currentUser != null )
{
/* do stuff here */
}
else
{
/* do something else, like show an error message perhaps */
}