我有这两门课:
public class Contratos
{
//...
public int EntidadeFinanceiraId { get; set; }
[Column("Nome")]
public EntidadesFinanceiras entidadeFinanceira { get; set; }
//...
}
public class EntidadesFinanceiras
{
[Key]
public int ID { get; set; }
public string Nome { get; set; }
//...
}
并希望根据 Contratos.entidade Financeira.Nome 动态过滤 Contratos 列表。这是根据用户选择的属性过滤列表的方法的一部分。
public IQueryable<Models.Contratos> applyLambdaFilter(string val, string col, string oper, IQueryable<Models.Contratos> contratosList)
{
if (!string.IsNullOrWhiteSpace(val))
{
string typeName;
string columnName;
Type propType;
string[] propName = col.Split(new[] { '.' });
if (propName.Count() > 1)
{
typeName = "GAcordos.Models." + propName[0]; //entidadeFinanceira
columnName = propName[1]; //Nome
propType = Type.GetType("GAcordos.Models.Contratos").GetProperty(propName[0]).PropertyType.GetProperty(columnName).PropertyType; //String
}
else
{
typeName = "GAcordos.Models.Contratos";
columnName = propName[0]; //Other Contratos property
propType = Type.GetType(typeName).GetProperty(columnName).PropertyType;
}
if (propType != null)
{
var fixedItem = Comparators.getFixedItemWithType(val, propType);
var param = Expression.Parameter(typeof(GAcordos.Models.Contratos), "x");
var body = Expression.Equal(Expression.PropertyOrField(param, col.ToString()), fixedItem, false, Type.GetType("GAcordos.Helpers.Comparators").GetMethod(oper, new Type[] { propType, propType }));
var lambda = Expression.Lambda<Func<GAcordos.Models.Contratos, bool>>(body, param);
contratosList = contratosList.Where(lambda.Compile()).AsQueryable();
}
}
return contratosList;
}
当方法执行时会抛出异常“entidadeFinanceira.Nome”不是“GAcordos.Models.Contratos”类型的成员在线上
var body = Expression.Equal(Expression.PropertyOrField(param, col.ToString()), fixedItem, false, Type.GetType("GAcordos.Helpers.Comparators").GetMethod(oper, new Type[] { propType, propType }));
但如果我直接写出表达式:
contratosList = contratosList.Where(x => x.entidadeFinanceira.Nome == val);
效果很好。
那么,如何构建 lambda 表达式 x => x.property.property == constVal?