如何将下拉列表的选定值传递给查询以便它将返回过滤的记录？

本文介绍了如何将下拉列表的选定值传递给查询以便它将返回过滤的记录？的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述 我需要根据DropDownList选择从数据库中过滤和显示Google Map Markers。为此我需要将选定的DropDownList值传递给查询。 我应该在下面的代码中做什么来完成上述任务？ i need to Filter and display Google Map Markers from database based on DropDownList selection. for that I need to pass the selected value of DropDownList to the query.What should i do in the following code to do the above task?using System;using System.Collections.Generic;using System.Linq;using System.Web;using System.Web.UI;using System.Web.UI.WebControls;using System.Data;using System.Configuration;using System.Data.SqlClient;namespace trial2{ public partial class explore : System.Web.UI.Page { protected void Page_Load(object sender, EventArgs e) { if (!IsPostBack) { DropDownList1.DataBind(); ListItem liMainArea = new ListItem("Select", "-1"); DropDownList1.Items.Insert(0, liMainArea); DropDownList2.DataBind(); ListItem liSubArea = new ListItem("Select", "-1"); DropDownList2.Items.Insert(0, liSubArea); DropDownList3.DataBind(); ListItem liAmenities = new ListItem("Select", "-1"); DropDownList3.Items.Insert(0, liAmenities); DropDownList2.Enabled = false; DropDownList3.Enabled = false; } if(!this.IsPostBack) { DataTable dt = this.GetData("select [Name], [Latitude], [Longitude] from [MAIN AREA]"); rptMarkers.DataSource = dt; rptMarkers.DataBind(); } } private DataTable GetData(string query) { string conString = ConfigurationManager.ConnectionStrings["gisConnectionString"].ConnectionString; SqlCommand cmd = new SqlCommand(query); using (SqlConnection con = new SqlConnection(conString)) { using (SqlDataAdapter sda = new SqlDataAdapter()) { cmd.Connection = con; sda.SelectCommand = cmd; using (DataTable dt = new DataTable()) { sda.Fill(dt); return dt; } } } } protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e) { if (DropDownList1.SelectedIndex == 0) { DropDownList2.Enabled = false; DropDownList2.DataBind(); ListItem liSubArea = new ListItem("Select", "-1"); DropDownList2.Items.Insert(0, liSubArea); DropDownList3.Enabled = false; DropDownList3.DataBind(); ListItem liAmenities = new ListItem("Select", "-1"); DropDownList3.Items.Insert(0, liAmenities); } else { DropDownList2.Enabled = true; DropDownList2.DataBind(); ListItem liSubArea = new ListItem("Select", "-1"); DropDownList2.Items.Insert(0, liSubArea); DropDownList3.SelectedIndex = 0; DropDownList3.Enabled = false; } } protected void DropDownList2_SelectedIndexChanged(object sender, EventArgs e) { if (DropDownList2.SelectedIndex == 0) { DropDownList3.Enabled = false; DropDownList3.DataBind(); ListItem liAmenities = new ListItem("Select", "-1"); DropDownList3.Items.Insert(0, liAmenities); } else { DropDownList3.Enabled = true; DropDownList3.DataBind(); ListItem liAmenities = new ListItem("Select", "-1"); DropDownList3.Items.Insert(0, liAmenities); } } protected void DropDownList3_SelectedIndexChanged(object sender, EventArgs e) { } }} 推荐答案 private DataTable GetData(string query, params object[] queryParameters){ using (SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["gisConnectionString"].ConnectionString)) using (SqlCommand cmd = con.CreateCommand()) { if (queryParameters != null && queryParameters.Length != 0) { IFormatProvider provider = CultureInfo.InvariantCulture; for (int index = 0; index < queryParameters.Length; index++) { string name = "@P" + index; string placeholder = "{" + index + "}"; query = query.Replace(placeholder, name); cmd.Parameters.AddWithValue(name, queryParameters[index] ?? DBNull.Value); } } cmd.CommandText = query; using (SqlDataAdapter sda = new SqlDataAdapter(cmd)) { DataTable dt = new DataTable(); sda.Fill(dt); return dt; } }}DataTable dt = GetData( "select [Name], [Latitude], [Longitude] from [MAIN AREA]" + " where ({0} Is Null Or [Name] = {0})" + " And ({1} Is Null Or [Latitude] = {1})" + " And ({2} Is Null Or [Longitude] = {2})", DropDownList1.SelectedValue, DropDownList2.SelectedValue, DropDownList3.SelectedValue); DataTable dt = this.GetData("select [Name], [Latitude], [Longitude] from [MAIN AREA] WHERE [Name] ='" + DropDownList1.SelectedItem.Text+"'"); rptMarkers.DataSource = dt; rptMarkers.DataBind(); DataTable dt = this.GetData("select [Name], [Latitude], [Longitude] from [MAIN AREA]"); rptMarkers.DataSource = dt; rptMarkers.DataBind(); 以下 - with following-StringBuilder query=new StringBuilder("select [Name], [Latitude], [Longitude] from [MAIN AREA] where 1=1");if(DropDownList1.SelectedIndex>0){ query.Append(" and [Name]="+DropDownList1.SelectedValue.ToString());}if(DropDownList2.SelectedIndex>0){ query.Append(" and [Latitude]="+DropDownList2.SelectedValue.ToString());}if(DropDownList3.SelectedIndex>0){ query.Append(" and [Longitude]="+DropDownList3.SelectedValue.ToString());}DataTable dt = this.GetData(query);rptMarkers.DataSource = dt;rptMarkers.DataBind(); 希望，这有帮助！ 如果我错过了请告诉我：）Hope, it helps !If I have missed something, please let me know :) 这篇关于如何将下拉列表的选定值传递给查询以便它将返回过滤的记录？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！