WinForm 動態查詢

1. 使用場景

在對數據進行篩選, 包含多個篩選字段時適用.

2. 接口設計

    /// <summary>
    /// 定義可作為追加到 WHERE 子句的控件接口
    /// </summary>
    internal interface IWhereSentence
    {
        /// <summary>
        /// 當前控件名稱
        /// </summary>
        string Name { get; }

        /// <summary>
        /// 對應數據表中的字段名稱
 

        /// </summary>
        string FieldName { get; set; }

        /// <summary>
        /// 操作符
        /// </summary>
        string Operator { get; set; }

        /// <summary>
        /// 是否作為查詢條件
        /// </summary>
        bool AsQuery { get; set; }
    }

    /// <summary>
    /// 定義可追加到 WHERE 子句的控件泛型接口
 

    /// </summary>
    /// <typeparam name="T">值的類型</typeparam>
    internal interface IWhereSentence<T> : IWhereSentence
    {
        /// <summary>
        /// 實際值
        /// </summary>
        T Value { get; set; }
    }

3. 接口實現, 以常見的 DateTimePicker 和 Textox 控件舉例

• 自定義控件, 繼承框架提供的 DateTimePicker

  類和 IWhereSentence<DateTime> 接口:

  /// <summary>
  /// 可追加到查詢條件的日期選擇器
  /// </summary>
  public partial class QueryDataTimerPicker : DateTimePicker, IWhereSentence<DateTime>
  {
      public QueryDataTimerPicker() : base() { }
  
      /// <summary>
      /// 是否作為查詢條件
      /// </summary>
      [DisplayName("是否作為查詢條件")]
      public bool AsQuery { get; set; }
  
      /// <summary>
      /// 字段名
      /// </summary>
      [DisplayName("字段名稱")]
      public string FieldName { get; set; }
  
      /// <summary>
      /// 操作符
      /// </summary>
      [DisplayName("操作符")]
      public string Operator { get; set; }
  }

• 自定義控件,繼承框架提供的 TextBox 控件和 IWhereSentence<string> 接口. AsQuery屬性可根據文本框是否有值, 返回是否作為查詢條件, Value 屬性與文本框自身的 Text 屬性綁定

  /// <summary>
  /// 可追加到查詢條件的文本框
  /// </summary>
  public class QueryTextBox : TextBox, IWhereSentence<string>
  {
      private bool _asQuery;
      public QueryTextBox() : base() { }
  
      /// <summary>
      /// 是否作為查詢條件
      /// </summary>
      [DisplayName("是否作為查詢條件")]
      public bool AsQuery
      {
          get { return this._asQuery && !string.IsNullOrWhiteSpace(this.Text); }
          set { this._asQuery = value; }
      }
  
      /// <summary>
      /// 字段名
      /// </summary>
      [DisplayName("字段名稱")]
      public string FieldName { get; set; }
  
      /// <summary>
      /// 操作符
      /// </summary>
      [DisplayName("操作符")]
      public string Operator { get; set; }
  
      /// <summary>
      /// 實際值
      /// </summary>
      public string Value { get { return this.Text; } set { this.Text = value; } }
  }

4. 運用

將自定義控件放置在目標窗體上, 可在屬性窗口設置相關屬性:

• 定義查詢控件集合

  private IWhereSentence[] _queryControls;
  this._queryControls = new IWhereSentence[]
  {
      this.queryDataTimerPickerStart,
      this.queryDataTimerPickerEnd,
      this.queryTextBoxTemp
  };

• 獲取WHERE子句

      /// <summary>
      /// 根據查詢條件生成WHERE字符串, 用於SQL查詢
      /// </summary>
      /// <returns>包含WHERE的SQL字符串</returns>
      private string GetWhereString()
      {
          var builderInst = PooledStringBuilder.GetInstance();
          var builder = builderInst.Builder;
          builder.Append("WHERE ");
  
          using (var enumerator = this._queryControls.Where(p => p.AsQuery).GetEnumerator())
          {
              if (!enumerator.MoveNext())
              {
                  builder.Clear();
                  return builderInst.ToStringAndFree();
              }
              AppendWhere(builder, enumerator.Current);
  
              while (enumerator.MoveNext())
              {
                  builder.Append(" AND ");
                  AppendWhere(builder, enumerator.Current);
              }
          }
          return builderInst.ToStringAndFree();
      }
  
      /// <summary>
      /// 將當前查詢控件追加到WHERE字符串中
      /// </summary>
      /// <param name="builder"><see cref="StringBuilder"/>對象</param>
      /// <param name="item">當前查詢控件</param>
      private void AppendWhere(StringBuilder builder, IWhereSentence item)
      {
          builder.Append(item.FieldName);
          if (_formatRegex.IsMatch(item.Operator))
              builder.Append(" ").AppendFormat(item.Operator, $"‘ + @{item.Name} + ‘");
          else
              builder.Append(" ").Append(item.Operator).Append(" ").Append("@").Append(item.Name);
      }
  
      /// <summary>
      /// 獲取查詢參數實際值
      /// </summary>
      /// <returns>查詢參數組成的匿名對象</returns>
      private object GetQueryParam()
      {
          return new
          {
              queryDataTimerPickerStart = this.queryDataTimerPickerStart.Value,
              queryDataTimerPickerEnd = this.queryDataTimerPickerEnd.Value,
              queryTextBoxTemp = this.queryTextBoxTemp.Value
          };
      }

• 查詢

    var sql = "...";
    sql = sql + GetWhereString();
    var param = GetQueryParam();
    var result = conn.Query(sql, param);    //使用Dapper

5. 問題

• 當前接口的定義了操作符屬性, 在拼接SQL時, 未實現面對復雜運算符的情況, 目前支持 LIKE(‘{0}‘)運算符.
• 多個條件之間默認使用 AND 連接, 若要擴展到使用 OR 或者其他運算符, 可在IWhereSentence接口中添加屬性
• 針對SQL Server數據庫, 若要針對MySQL或Oracle等其他數據庫, 需更改SQL參數標識符 @.

WinForm動態查詢