[英]Why is one section of code working, but the other not?
这是有效的代码:
protected void submitForMail(object sender, EventArgs e)
{
string constr = @"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=|DataDirectory|\TravelJoansDB.mdb;";
string cmdstr = "INSERT INTO EmailList(FirstName,LastName,EmailAddress) VALUES (@FirstName, @LastName, @EmailAddress)";
OleDbConnection con = new OleDbConnection(constr);
OleDbCommand com = new OleDbCommand(cmdstr, con);
TextBox tFirstName = (TextBox)FormView1.FindControl("FirstName");
TextBox tLastName = (TextBox)FormView1.FindControl("LastName");
TextBox tEmail = (TextBox)FormView1.FindControl("EmailAddress");
con.Open();
com.Parameters.AddWithValue("@FirstName", tFirstName.Text);
com.Parameters.AddWithValue("@LastName", tLastName.Text);
com.Parameters.AddWithValue("@EmailAddress", tEmail.Text);
com.ExecuteNonQuery();
con.Close();
}
这是没有的代码:
protected void UpdatePic(object sender, EventArgs e)
{
string constr = @"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=|DataDirectory|\TravelJoansDB.mdb;";
string cmdstr = "INSERT INTO BlogEntryItems(Picture) VALUES (@UpdatedPic)";
OleDbConnection con = new OleDbConnection(constr);
OleDbCommand com = new OleDbCommand(cmdstr, con);
TextBox uPic = (TextBox)DataList1.FindControl("BEIPictureField");
con.Open();
com.Parameters.AddWithValue("@UpdatedPic", uPic.Text);
com.ExecuteNonQuery();
con.Close();
}
这是包含Datalist1控件的代码:
<asp:AccessDataSource ID="AccessDataSource1" runat="server"
DataFile="~/App_Data/TravelJoansDB.mdb"
SelectCommand="SELECT * FROM Table2 INNER JOIN [BlogEntryItems] ON Table2.ID=BlogEntryItems.BlogID WHERE ID=@ID" >
<SelectParameters>
<asp:QueryStringParameter Name="ID" QueryStringField="ID" />
</SelectParameters>
</asp:AccessDataSource>
<asp:DataList ID="DataList1" runat="server" DataSourceID="AccessDataSource1">
<ItemStyle />
<ItemTemplate>
<table>
<tr>
<td>
<br />
<asp:Image ID="Image1" CssClass="placePicCenter" runat="server"
BorderWidth="1px"
BorderColor="#EEEEEE"
ImageUrl='<%# "PlaceImages/" + Eval("Picture") %>' /><br />
<asp:TextBox ID="BEIPictureField" runat="server" Text='<%# Bind("Picture") %>' /><br />
<asp:Button ID="UpdatePicButton" runat="server" Text="Update" OnClick="UpdatePic" />
<br />
</td>
</tr>
<tr>
<td>
<asp:Label ID="Label4" CssClass="placeBodyStyle" runat="server" Text='<%# Eval("PicText1") %>' />
</td>
</tr>
<tr>
<td>
</td>
</tr>
</table>
</ItemTemplate>
</asp:DataList>
这些代码块用于两个不同页面上的两个不同按钮。 运行第二段代码时出现的错误是“对象引用未设置为对象的实例”。 任何帮助,将不胜感激。
此行是可能的原因,它找不到控件BEIPictureField,因此“对象引用未设置为对象的实例”。 错误
TextBox uPic = (TextBox)DataList1.FindControl("BEIPictureField");
编辑1
尝试这个:
TextBox uPic = (TextBox)DataList1.Items[1].FindControl("BEIPictureField");
您将不得不重写逻辑以在每个项目中而不是在DataList中找到控件,因为它是父级,您将无法在其中找到它。
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