标签：opera rem exce stat 值类型 数据 field 必须 info
/// <summary>/// 获取查询表达式树 (zuowenjun.cn)/// </summary>/// <typeparam name="TEntity"></typeparam>/// <param name="fieldName"></param>/// <param name="operatorName"></param>/// <param name="value"></param>/// <param name="value2"></param>/// <returns></returns>public static Expression<Func<TEntity, bool>> GetQueryExpression<TEntity>(string fieldName, string operatorName, string value, string value2) where TEntity : class{ PropertyInfo fieldInfo = typeof(TEntity).GetProperty(fieldName, BindingFlags.Instance | BindingFlags.Public | BindingFlags.IgnoreCase); Type pType = fieldInfo.PropertyType; if (string.IsNullOrEmpty(operatorName)) { throw new ArgumentException("运算符不能为空！", "operatorName"); } dynamic convertedValue; if (!value.TryChangeType(pType, out convertedValue)) { throw new ArgumentException(string.Format("【{0}】的查询值类型不正确,必须为{1}类型！", General.GetDisplayName(fieldInfo), pType.FullName), "value"); } ParameterExpression expParameter = Expression.Parameter(typeof(TEntity), "f"); MemberExpression expl = Expression.Property(expParameter, fieldInfo); ConstantExpression expr = Expression.Constant(convertedValue, pType); Expression expBody = null; Type expType = typeof(Expression); var expMethod = expType.GetMethod(operatorName, new[] { expType, expType }); if (expMethod != null) { expBody = (Expression)expMethod.Invoke(null, new object[] { expl, expr }); } else if (FilterOperators.Between == operatorName) { dynamic convertedValue2; if (!value2.TryChangeType(pType, out convertedValue2)) { throw new ArgumentException(string.Format("【{0}】的查询值2类型不正确,必须为{1}类型！", General.GetDisplayName(fieldInfo), pType.FullName), "value"); } ConstantExpression expr2 = Expression.Constant(convertedValue2, pType); expBody = Expression.GreaterThanOrEqual(expl, expr); expBody = Expression.AndAlso(expBody, Expression.LessThanOrEqual(expl, expr2)); } else if (new[] { FilterOperators.Contains, FilterOperators.StartsWith, FilterOperators.EndsWith }.Contains(operatorName)) { expBody = Expression.Call(expl, typeof(string).GetMethod(operatorName, new Type[] { typeof(string) }), expr); } else { throw new ArgumentException("无效的运算符！", "operatorName"); } Expression<Func<TEntity, bool>> lamExp = Expression.Lambda<Func<TEntity, bool>>(expBody, expParameter); return lamExp;}标签：opera rem exce stat 值类型 数据 field 必须 info
原文地址：http://www.cnblogs.com/shitaotao/p/7648259.html
