public ResultService <Expression <Func <T, bool> > > BuildExpression()
{
try
{
ParameterExpression parameterExpression = Expression.Parameter(typeof(T), "x");
Expression finalExpression = Expression.Constant(true);
foreach (var statement in _filterStatements)
{
if (!statement.IsValid)
{
return(ResultService.Fail <Expression <Func <T, bool> > >(ErrorCode.EntityNotValid));
}
Type propType = typeof(T).GetProperty(statement.PropertyName).PropertyType;
TypeConverter converter = TypeDescriptor.GetConverter(propType);
object convertedObject = converter.ConvertFrom(statement.Value);
var member = Expression.Property(parameterExpression, statement.PropertyName);
var constant = Expression.Constant(convertedObject);
Expression expression = null;
switch (statement.Operation)
{
case FilterOperation.Equal:
expression = Expression.Equal(member, constant);
break;
case FilterOperation.Contains:
throw new NotImplementedException();
//break;
case FilterOperation.StartsWith:
throw new NotImplementedException();
//break;
case FilterOperation.EndsWith:
throw new NotImplementedException();
//break;
case FilterOperation.NotEqual:
expression = Expression.NotEqual(member, constant);
break;
case FilterOperation.GreaterThan:
expression = Expression.GreaterThan(member, constant);
break;
case FilterOperation.GreaterThanOrEqual:
expression = Expression.GreaterThanOrEqual(member, constant);
break;
case FilterOperation.LessThan:
expression = Expression.LessThan(member, constant);
break;
case FilterOperation.LessThanOrEqual:
expression = Expression.LessThanOrEqual(member, constant);
break;
default:
throw new NotImplementedException();
//break;
}
;
finalExpression = Expression.AndAlso(finalExpression, expression);
}
Expression <Func <T, bool> > result = Expression.Lambda <Func <T, bool> >(finalExpression, parameterExpression);
return(ResultService.Ok <Expression <Func <T, bool> > >(result));
}
catch (Exception ex)
{
return(ResultService.Fail <Expression <Func <T, bool> > >(ex));
}
}