使用ASP.NET C＃進行高級搜索過濾

Question

我正在嘗試創建高級搜索查詢，該查詢允許用戶輸入所需的任意數量的過濾器。 該過濾器包含不同的Asp控件，例如dropdownlist和checkbox。 這是我使用的查詢，問題是它需要輸入所有過濾器才能工作，我需要它接受任何過濾器集合。

此查詢僅工作一個按鈕。 （請在修改我的代碼后發布您的答案，以便更好地理解。

稍后我將對查詢進行參數化。

 public partial class Searchpage : System.Web.UI.Page
 {
    SqlConnection con = new SqlConnection();
    string price1;
    string price2;
    string osx;
    string checktwog;
    string checkthreeg;
    string checkfourg;
    string phonetype;
    string cam;
    string ram;
    string q;
    protected void Page_Load(object sender, EventArgs e)
    {
        con.ConnectionString = ConfigurationManager.ConnectionStrings["conn"].ConnectionString;
    con.Open();
    try
    {
        price1 = Convert.ToString(Session["price1"]);
        price2 = Convert.ToString(Session["price2"]);
        osx = Convert.ToString(Session["osx"]);
        checktwog = Convert.ToString(Session["checktwog"]);
        checkthreeg = Convert.ToString(Session["checkthreeg"]);
        checkfourg = Convert.ToString(Session["checkfourg"]);
        phonetype = Convert.ToString(Session["phonetype"]);
        cam = Convert.ToString(Session["cam"]);
        ram = Convert.ToString(Session["ram"]);
        q = "select * from legacy where price >= " + price1 + " and price <= " + price2 + " and os = '" + osx + "' and gprsedge = '" + checktwog + "' and threeg= '" + checkthreeg + "' and fourg='" + checkfourg + "' and touchscreen='" + phonetype + "' and camera='" + cam + "' and ram='" + ram +"'";
        SqlDataSource1.SelectCommand = q;
        SqlDataSource1.DataBind();

Answer 1

你可以做類似的事情（代碼未經測試）

List<string> conditions = new List<string>();
if (price1 != null)
{
    cmd.Parameters.Add("@param1", price);
    conditions.Add(" price >= @param1 ");
}

if (price2 != null)
{
    cmd.Parameters.Add("@param2");
    conditions.Add(" price <= @param2 ");
}

.....

StringBuilder sb = new StringBuilder();
sb.Append("select * from legacy ");
if(conditions.Count > 0)
{
    sb.Append("WHERE ");
    sb.Append(string.Join(" AND ", conditions));
}

Answer 2

檢查以下算法

var filters = new List<filterItem>();
filters.Add(new filterItem(field: "price", op: ">=", value: Session["price1"]));
filters.Add(new filterItem(field: "price", op: "<=", value: Session["price2"]));
filters.Add(new filterItem(field: "os", op: "=", value: Session["osx"]));
filters.Add(new filterItem(field: "gprsedge", op: "=", value: Session["checktwog"]));
filters.Add(new filterItem(field: "threeg", op: "=", value: Session["checkthreeg"]));
filters.Add(new filterItem(field: "fourg", op: "=", value: Session["checkfourg"]));
filters.Add(new filterItem(field: "touchscreen", op: "=", value: Session["phonetype"]));
filters.Add(new filterItem(field: "camera", op: ">=", value: Session["cam"]));
filters.Add(new filterItem(field: "ram", op: ">=", value: Session["ram"]));

var conditions = filters
    .Where(f => f.Value != null)
    .Select((filter, index) => {
        var parameterName = string.Format("p{0}", index);// eg: p0, p1, ...
        var parameterValue = Convert.ToString(filter.Value);
        //Add parameter to SelectParameters
        SqlDataSource1.SelectParameters.Add(parameterName, parameterValue);
        //Construct filter for query, eg price >= @p0
        var condition = string.Format("{0} {1} @{2}", filter.Field, filter.Operator, parameterName);
        return condition;
    });

var predicate = string.Empty;
if (conditions.Count() > 0) {
    predicate = string.Format("WHERE {0}", string.Join(" AND ", conditions));
}

var query = "SELECT * FROM legacy";

var selectCommand = string.Join(" ", query, predicate).Trim();

SqlDataSource1.SelectCommand = selectCommand;

其中filterItem類型定義為

class filterItem {
    public filterItem(string field, string op, object value) {
        this.Field = field;
        this.Operator = op;
        this.Value = value;
    }
    public string Field { get; private set; }
    public string Operator { get; private set; }
    public object Value { get; private set; }
}