根据数据库设置 DropDownList 的 SelectValue

Question

我在 GridView 中有一个 DropDownList，我希望选择的值是该特定人在数据库中的任何值

我的 DropDownList 的 ASP 代码：

<asp:TemplateField HeaderText="Team" SortExpression="Team">
                <ItemTemplate>
                    <asp:DropDownList ID="ddlTeam" runat="server" 
                   DataSourceID="SqlDataSource1" DataTextField="Team" 
                        DataValueField="Team" ondatabound="ddlTeam_DataBound">
                    </asp:DropDownList>
                    <asp:SqlDataSource ID="SqlDataSource2" runat="server" 
                        ConnectionString="<%$ ConnectionStrings:connectionString %>" 
                        SelectCommand="SELECT DISTINCT [Team] FROM [Team_Names]"></asp:SqlDataSource>
                </ItemTemplate>
            </asp:TemplateField>

我的 ddlTeam_OnBound：

protected void ddlTeam_DataBound(object sender, EventArgs e)
        {
            DropDownList ddl = (DropDownList)sender;
            foreach (ListItem item in ddl.Items)
            {
                if (item.Text == "valor")
                {
                    item.Text = "Team Valor";
                }
                else if (item.Text == "mystic")
                {
                    item.Text = "Team Mystic";
                }
            }
        }

更新 - 没有错误但 DDL 为空：

    DropDownList ddl = new DropDownList();
                string query2 = "SELECT team_name FROM sec WHERE job = " + TextBox1.Text;
                using (SqlConnection con = new SqlConnection(connectionString))
                {
                    using (SqlCommand cmd = new SqlCommand(query2, con))
                    {
                        con.Open();
                        using (SqlDataReader read = cmd.ExecuteReader())
                        {
                        while(read.Read())
                        {
                            ddl.SelectedValue = read["team_name"].ToString();
                        }
                        }
                        con.Close();
                    }
                }

Answer 1

在SqlDataSource 的查询中执行所有操作，并且不要在没有必要的情况下使用后面的代码。

<asp:TemplateField HeaderText="Team" SortExpression="Team">
    <ItemTemplate>
        <asp:DropDownList ID="ddlTeam" runat="server" 
       DataSourceID="SqlDataSource1" DataTextField="Team_txt" 
            DataValueField="Team"><%--No need  ondatabound="ddlTeam_DataBound"--%>
        </asp:DropDownList><%--datasourceId must match --%>
        <asp:SqlDataSource ID="SqlDataSource1" runat="server" 
            ConnectionString="<%$ ConnectionStrings:connectionString %>" 
            SelectCommand="SELECT DISTINCT [Team],case Team when 'valor' then 'Team Valor' when 'mystic' then 'Team Mystic' else Team end team_txt FROM [Team_Names]"></asp:SqlDataSource>
    </ItemTemplate>
</asp:TemplateField>

Answer 2

您没有执行 SqlCommand 或打开 SqlConnection。您应该将输入放入参数中以防止潜在的 SQL 注入攻击。

举个例子：

            string teamName = string.Empty;
            using (SqlConnection connection = new SqlConnection("your connection string"))
            {
                connection.Open();

                string query = "SELECT DISTINCT team_name FROM sec WHERE job = @job";
                SqlParameter param = new SqlParameter
                {
                    ParameterName = "@job",
                    Value = TextBox1.Text
                };

                using (SqlCommand command = new SqlCommand(query, connection))
                {
                    command.Parameters.Add(param);
                    SqlDataReader reader = command.ExecuteReader(CommandBehavior.SingleRow);

                    if (reader.Read())
                    {
                        teamName = reader.GetString(0);
                        // or
                        int ord = reader.GetOrdinal("team_name");
                        teamName = reader.GetString(ord); // Handles nulls and empty strings.
                    }
                }
            }

编辑

您还必须正确设置下拉列表。

 DropDownList ddl = new DropDownList();
 ddl.DataSource = // call your database code - see above
 ddl.DataValueField = "ValueProperty";
 ddl.DataTextField = "TextProperty";
 ddl.DataBind();

 ddl.SelectedValue = teamName;