public Expression GetFilterExpression(ParameterExpression itemPram, FilterComparisonOperator comparisonOperator, string valueString)
{
var getterMemberExpr = _reader.GetSelectExpression(itemPram);
if (getterMemberExpr == null)
{
throw new InvalidCastException("Getter expression returned from IFieldReader is not of type MemberExpression.");
}
object valueObj = ConversionUtility.ConvertString(valueString, _reader.FieldType);
ConstantExpression variableExpression = Expression.Constant(valueObj, _reader.FieldType); // TODO variable not constant?
var operatorMethod = GetOperatorExpressionMethod(comparisonOperator);
Expression predicateExpression = operatorMethod.Invoke(getterMemberExpr, variableExpression);
return(predicateExpression);
}
private static Func <Expression, ConstantExpression, Expression> GetOperatorExpressionMethod(FilterComparisonOperator comparisonOperator)
{
switch (comparisonOperator)
{
case FilterComparisonOperator.Equals:
return(Expression.Equal);
case FilterComparisonOperator.NotEquals:
return(Expression.NotEqual);
case FilterComparisonOperator.GreaterThan:
return(Expression.GreaterThan);
case FilterComparisonOperator.GreaterThanOrEquals:
return(Expression.GreaterThanOrEqual);
case FilterComparisonOperator.LessThan:
return(Expression.LessThan);
case FilterComparisonOperator.LessThanOrEquals:
return(Expression.LessThanOrEqual);
case FilterComparisonOperator.Contains:
return(ExpressionCallComparisonMethod("Contains"));
case FilterComparisonOperator.StartsWith:
return(ExpressionCallComparisonMethod("StartsWith"));
case FilterComparisonOperator.EndsWith:
return(ExpressionCallComparisonMethod("EndsWith"));
case FilterComparisonOperator.IsIn:
return(ExpressionCallComparisonMethod("Contains", true));
default:
throw new ArgumentOutOfRangeException(nameof(comparisonOperator), comparisonOperator, null);
}
}
public FilterInstruction(string fieldName, FilterComparisonOperator comparisonOperator, string valueString)
{
FieldName = fieldName;
Operator = comparisonOperator;
ValueString = valueString;
}
public Expression GetFilterExpression(ParameterExpression itemPram, FilterComparisonOperator comparisonOperator, string valueString)
{
throw new NotSupportedException("Filtering is not supported for " + _resourceType + ".");
}
