下拉列表名称有一个无效的 SelectedValue，因为它不存在于项目列表中

Question

我想要实现的是当我单击编辑时，gridview 中的 Blogtype 字段将更改为下拉列表。而且由于我的数据库在博客类型中有3个数据，分别是社区工作、竞争和海外经验。下拉列表将允许我选择这三个中的任何一个。选择其中一个后，我单击更新，它将在数据库中更新。怎么做，因为我在第三个屏幕截图中有错误。我的 blogtype 字段下拉列表的名称是 ddlBlogType。帮助

但是对于我目前的代码，点击编辑后，会出现这个错误。 “ddlBlogType”有一个无效的 SelectedValue，因为它不存在于项目列表中。 参数名称：值

源代码

<asp:GridView ID="grdBlog" runat="server" style=
"margin-left: 0px" Width="1000px" Height="147px" AutoGenerateColumns="False" 
                        onrowcancelingedit="grdBlog_RowCancelingEdit" onrowediting="grdBlog_RowEditing" 
                        onrowupdating="grdBlog_RowUpdating" DataKeyNames="BlogID" 
                        onrowdeleting="grdBlog_RowDeleting" AllowPaging="True" 
                        onpageindexchanging="grdBlog_PageIndexChanging" PageSize="5" 
            BackColor="White" BorderColor="White" BorderStyle="Ridge" BorderWidth="2px" 
            CellPadding="3" CellSpacing="1" GridLines="None" >
                        <Columns>
                            <asp:BoundField DataField="BlogID" HeaderText="BlogID" ReadOnly="true" 
                                SortExpression="BlogID" />
                            <asp:TemplateField HeaderText="Name">
                                <EditItemTemplate>
                                    <asp:TextBox ID="txtName" runat="server" Width="80px" Text='<%# Bind("Name") %>'></asp:TextBox>
                                </EditItemTemplate>
                                <ItemTemplate>
                                    <asp:Label ID="Label1" runat="server" Text='<%# Bind("Name") %>'></asp:Label>
                                </ItemTemplate>
                            </asp:TemplateField>
                            <asp:TemplateField HeaderText="BlogType">
                                <EditItemTemplate>
                                    <asp:DropDownList ID="ddlBlogType" runat="server" Width="80px" Text='<%# Bind("BlogType") %>'></asp:DropDownList>
                                </EditItemTemplate>
                                <ItemTemplate>
                                    <asp:Label ID="Label2" runat="server" Text='<%# Bind("BlogType") %>'></asp:Label>
                                </ItemTemplate>
                            </asp:TemplateField>
                            <asp:TemplateField HeaderText="Description">
                                <EditItemTemplate>
                                    <asp:TextBox ID="txtDescription" runat="server" Width="80px" Text='<%# Bind("Description") %>'></asp:TextBox>
                                </EditItemTemplate>
                                <ItemTemplate>
                                    <asp:Label ID="Label3" runat="server" Text='<%# Bind("Description") %>'></asp:Label>
                                </ItemTemplate>
                            </asp:TemplateField>
                            <asp:BoundField DataField="DateEntry" HeaderText="Date Entry" ReadOnly="true" />
                            <asp:TemplateField HeaderText="Blog Story">
                                <EditItemTemplate>
                                    <asp:TextBox ID="txtBlogStory" runat="server" TextMode="multiline" rows="10" Text='<%# Bind("BlogStory") %>'></asp:TextBox>
                                </EditItemTemplate>
                                <ItemTemplate>
                                    <asp:Label ID="Label5" runat="server" Text='<%# Bind("BlogStory") %>'></asp:Label>
                                </ItemTemplate>
                            </asp:TemplateField>
                            <asp:BoundField DataField="modifiedby" HeaderText="Last Modified By" ReadOnly="true" />
                            <asp:BoundField DataField="modifieddate" HeaderText="Last Modified Date" ReadOnly="true" />
                            <asp:CommandField ShowEditButton="True" CausesValidation="false" />
                            <asp:TemplateField ShowHeader="False">
                                <ItemTemplate>
                                    <asp:LinkButton ID="LinkButton1" runat="server" CausesValidation="False" 
                                        CommandName="Delete" Text="Delete" OnClientClick="javascript : return confirm('Confirm delete this record?');"></asp:LinkButton>
                                </ItemTemplate>
                            </asp:TemplateField>
                        </Columns>
                        <FooterStyle BackColor="#C6C3C6" ForeColor="Black" />
                        <HeaderStyle BackColor="#4A3C8C" Font-Bold="True" ForeColor="#E7E7FF" />
                        <PagerStyle BackColor="#C6C3C6" ForeColor="Black" HorizontalAlign="Right" />
                        <RowStyle BackColor="#DEDFDE" ForeColor="Black" />
                        <SelectedRowStyle BackColor="#9471DE" Font-Bold="True" ForeColor="White" />
                        <SortedAscendingCellStyle BackColor="#F1F1F1" />
                        <SortedAscendingHeaderStyle BackColor="#594B9C" />
                        <SortedDescendingCellStyle BackColor="#CAC9C9" />
                        <SortedDescendingHeaderStyle BackColor="#33276A" />
                    </asp:GridView>

代码背后的代码

if (Page.IsPostBack == false)
        {
            bindResultGridView();

        }

 private void bindResultGridView()
    {
        String ConStr = ConfigurationManager.ConnectionStrings["BlogConnectionString"].ConnectionString;
        SqlConnection con = new SqlConnection(ConStr);

        try
        {

            String SQL = null;

            SQL = "SELECT BlogID, Name, Blogtype, Description, convert(varchar,Dateentry, 103) as Dateentry, BlogStory, modifiedby, convert(varchar,modifieddate, 103) as modifieddate FROM [EntryTable] ORDER BY BlogID DESC";

            SqlCommand cmd = new SqlCommand(SQL, con);
            con.Open();

            SqlDataReader reader = cmd.ExecuteReader();
            DataTable dt = new DataTable();
            dt.Load(reader);
            grdBlog.DataSource = dt;
            grdBlog.DataBind();


            reader.Close();
        }

        finally
        {
            con.Close();
        }
    }

 protected void grdBlog_RowCancelingEdit(object sender, GridViewCancelEditEventArgs e)
    {
        grdBlog.EditIndex = -1;
        bindResultGridView();
    }

    protected void grdBlog_RowEditing(object sender, GridViewEditEventArgs e)
    {
        grdBlog.EditIndex = e.NewEditIndex;
        bindResultGridView();
    }
    protected void grdBlog_RowUpdating(object sender, GridViewUpdateEventArgs e)
    {
        int selectedRow = e.RowIndex;   //get selected row
        //  get product id from data key
        int blogid = (int)grdBlog.DataKeys[selectedRow].Value;

        //  get current grid view row
        GridViewRow row = (GridViewRow)grdBlog.Rows[selectedRow];
        TextBox name = (TextBox)row.FindControl("txtName");
        //  find text box for txtPrice
        DropDownList blogtype = (DropDownList)row.FindControl("ddlBlogType");
        TextBox description = (TextBox)row.FindControl("txtDescription");
        TextBox blogstory = (TextBox)row.FindControl("txtBlogStory");
        //  Remove $ sign
        string strName = name.Text;
        string strBlogType = blogtype.Text;
        string strDescription = description.Text;
        string strBlogStory = blogstory.Text;
        /*
        DateTime datDate;
        */

        /*
        if (DateTime.TryParseExact(strDateEntry, new string[] { "dd/MM/yyyy" },
                               System.Globalization.CultureInfo.InvariantCulture,
                               System.Globalization.DateTimeStyles.None, out datDate))
        {
         */
            updateBlogGridviewRecord(blogid, strName, strBlogType, strDescription, strBlogStory);
        /*
        }

        else
        {
            lblError.Visible = true;
            lblError.Text = "Invalid Date";
            lblSuccess.Visible = false;
        }
        */
    }

        private void updateBlogGridviewRecord(int blogid, string strName, string strBlogType, string strDescription, string strBlogStory)
        {
            try
            {
                string strConnectionString = ConfigurationManager.ConnectionStrings["BlogConnectionString"].ConnectionString;
                SqlConnection myConnect = new SqlConnection(strConnectionString);

                string strCommandText = "UPDATE EntryTable SET [ModifiedBy]=@Modifier, [ModifiedDate] = GETDATE(), [Name]=@Name, [BlogType]=@BlogType, [Description]=@Description, [BlogStory]=@BlogStory WHERE [BlogID]=@BlogID";
                /*string strCommandText = "UPDATE EntryTable SET [Name]=@Name, [BlogType]=@BlogType, [Description]=@Description, [DateEntry]=@DateEntry, [BlogStory]=@BlogStory WHERE [BlogID]=@BlogID"; */
                /*string strCommandText = "UPDATE EntryTable SET [ModifiedBy] = [Name], [Name]=@Name, [BlogType]=@BlogType, [Description]=@Description, [DateEntry]=@DateEntry, [BlogStory]=@BlogStory WHERE [BlogID]=@BlogID"; */

                SqlCommand cmd = new SqlCommand(strCommandText, myConnect);
                cmd.Parameters.AddWithValue("@BlogID", blogid);
                cmd.Parameters.AddWithValue("@Name", strName);
                cmd.Parameters.AddWithValue("@BlogType", strBlogType);
                //cmd.Parameters.AddWithValue("@DateEntry", datDate);
                cmd.Parameters.AddWithValue("@Description", strDescription);
                cmd.Parameters.AddWithValue("@BlogStory", strBlogStory);
                cmd.Parameters.AddWithValue("@Modifier", Session["Username"]);
                myConnect.Open();

                int result = cmd.ExecuteNonQuery();

                if (result > 0)
                {
                    lblSuccess.Visible = true;
                    lblSuccess.Text = "Record updated!";
                    lblError.Visible = false;
                }
                else
                {
                    lblSuccess.Visible = true;
                    lblError.Text = "Update fail";
                    lblError.Visible = false;
                }

                myConnect.Close();


                //Cancel Edit Mode
                grdBlog.EditIndex = -1;
                bindResultGridView();
            }

            catch
            {
                lblError.Visible = true;
                lblError.Text = "Invalid Data";
                lblSuccess.Visible = false;
            }
        }

使用下面的编辑代码来做吗

源代码

                            <asp:TemplateField HeaderText="BlogType">
                                <EditItemTemplate>
                                <asp:DropDownList ID="ddlBlogType" runat="server" DataTextField="ddlBlogType" DataValueField="ddlBlogType" SelectedValue='<%# Eval("blogType") %>'>                                                                 
                                    <asp:ListItem Enabled="true" Text="Community Work" Value="Community Work"></asp:ListItem>
                                    <asp:ListItem Text="Competition" Value="Competition"></asp:ListItem>
                                    <asp:ListItem Text="Overseas Experience" Value="Overseas Experience"></asp:ListItem>
                                </asp:DropDownList>
                                </EditItemTemplate>
                                <ItemTemplate>
                                    <asp:Label ID="Label2" runat="server" Text='<%# Bind("BlogType") %>'></asp:Label>
                                </ItemTemplate>
                            </asp:TemplateField>

代码背后的代码

 protected void grdBlog_RowUpdating(object sender, GridViewUpdateEventArgs e)
    {
        int selectedRow = e.RowIndex;   //get selected row
        //  get product id from data key
        int blogid = (int)grdBlog.DataKeys[selectedRow].Value;

        //  get current grid view row
        GridViewRow row = (GridViewRow)grdBlog.Rows[selectedRow];
        TextBox name = (TextBox)row.FindControl("txtName");
        //  find text box for txtPrice
        DropDownList blogtype = (DropDownList)row.FindControl("ddlBlogType");
        TextBox description = (TextBox)row.FindControl("txtDescription");
        TextBox blogstory = (TextBox)row.FindControl("txtBlogStory");
        //  Remove $ sign
        string strName = name.Text;
        string strBlogType = blogtype.SelectedValue;
        string strDescription = description.Text;
        string strBlogStory = blogstory.Text;
    }

Answer 1

我认为问题在于您填充 DropDownList 的方式。该代码未显示在您的帖子中，因此假设您没有任何效果。

所以你通常在编辑模式下设置所需的gridviewrow，如下所示：

protected void grdBlog_RowEditing(object sender, GridViewEditEventArgs e)
{
    grdBlog.EditIndex = e.NewEditIndex;
    bindResultGridView();
}

现在我们需要确定何时绑定下拉列表。因此，当特定数据行（处于编辑模式）正在获取数据绑定时，我们有机会获得对相应编辑行下拉列表的引用。因此，您可以参考this 帖子。

总而言之，您需要处理 gridview 的 DataBound 事件并从它的 rowstate 确定它处于什么模式。从下面的链接帖子中分享代码示例：

protected void gv_RowDataBound(object sender, GridViewEditEventArgs e)
{
    if (e.Row.RowType == DataControlRowType.DataRow)
    {
        if ((e.Row.RowState & DataControlRowState.Edit) > 0)
        {
            DropDownList ddList= (DropDownList)e.Row.FindControl("DStatusEdit");
            //bind dropdownlist
            DataTable dt = con.GetData("select distinct status from directory");
            ddList.DataSource = dt;
            ddList.DataTextField = "YourCOLName";
            ddList.DataValueField = "YourCOLName";
            ddList.DataBind();

            DataRowView dr = e.Row.DataItem as DataRowView;
            //ddList.SelectedItem.Text = dr["YourCOLName"].ToString();
            ddList.SelectedValue = dr["YourCOLName"].ToString();
        }
   }
}