I implemented an extension method ApplyFilter like this:
public static IQueryable<T> ApplyFilter<T>(this IQueryable<T> query, FilterNode filter)
{
if (filter == null)
return query;
// Create a parameter expression for the queryable entity
ParameterExpression parameter = Expression.Parameter(typeof(T), "entity");
List<FilterNode> filters = new List<FilterNode>() { filter };
// Build the predicate expression
Expression<Func<T, bool>> predicate = BuildPredicate<T>(filters, parameter);
// Apply the predicate to the query
return query.Where(predicate);
}
private static Expression<Func<T, bool>> BuildPredicate<T>(List<FilterNode> filters, ParameterExpression parameter)
{
Expression combinedExpression = null;
foreach (var filter in filters)
{
Expression filterExpression;
if (filter is FilterCriteriaNode criteriaNode)
{
filterExpression = BuildCriteriaExpression(criteriaNode, parameter);
}
else if (filter is FilterGroupNode groupNode)
{
filterExpression = BuildGroupExpression<T>(groupNode, parameter);
}
else
{
throw new ArgumentException($"Unknown filter node type: {filter.GetType().Name}");
}
if (filterExpression != null)
{
combinedExpression = combinedExpression == null
? filterExpression
: (filter.Operator == LogicalOperator.Or
? Expression.OrElse(combinedExpression, filterExpression)
: Expression.AndAlso(combinedExpression, filterExpression));
}
}
return combinedExpression == null ? null : Expression.Lambda<Func<T, bool>>(combinedExpression, parameter);
}
private static Expression BuildCriteriaExpression(FilterCriteriaNode criteriaNode, ParameterExpression parameter)
{
string[] propertyNames = criteriaNode.FieldName.Split('.');
Expression propertyAccess = parameter;
foreach (string propertyName in propertyNames)
{
propertyAccess = Expression.Property(propertyAccess, propertyName);
}
Expression propertyExpression = propertyAccess;
Type propertyType = propertyExpression.Type;
// If the property is nullable, handle the null checks
if (propertyType.IsGenericType && propertyType.GetGenericTypeDefinition() == typeof(Nullable<>))
{
propertyExpression = Expression.Property(propertyExpression, "Value");
propertyType = Nullable.GetUnderlyingType(propertyType);
}
// Convert the constant value to the appropriate type
Expression constant;
if (criteriaNode.Operator == ComparisonOperator.Any || criteriaNode.Operator == ComparisonOperator.Between)
{
// Split the string value by comma and convert each part to the appropriate type
string[] parts = criteriaNode.Value.Split(',');
var constantValues = parts.Select(part => string.IsNullOrEmpty(part) ? null : Convert.ChangeType(part.Trim(), propertyType)).ToArray();
if (criteriaNode.Operator == ComparisonOperator.Between)
{
// For "Between" operator, constantValues is an array with two elements
var min = Expression.Constant(constantValues[0], propertyType);
var max = Expression.Constant(constantValues[1], propertyType);
return Expression.AndAlso(
Expression.GreaterThanOrEqual(propertyExpression, min),
Expression.LessThanOrEqual(propertyExpression, max)
);
}
else // For "Any" operator
{
// Get the underlying type of the property
Type propertyUnderlyingType = propertyType;
if (propertyType.IsGenericType && propertyType.GetGenericTypeDefinition() == typeof(Nullable<>))
{
propertyUnderlyingType = Nullable.GetUnderlyingType(propertyType);
}
// Convert constantValue to IEnumerable<T>
var convertedValue = ((IEnumerable)constantValues).Cast<object>().Select(x => Convert.ChangeType(x, propertyUnderlyingType)).ToArray();
// Create array initializer expression
var arrayInitializer = convertedValue.Select(x => Expression.Constant(x, propertyUnderlyingType));
// Create array expression using array initializer
var arrayExpression = Expression.NewArrayInit(propertyUnderlyingType, arrayInitializer);
// Call the Contains method
var containsMethod = typeof(Enumerable).GetMethods()
.First(m => m.Name == "Contains" && m.GetParameters().Length == 2)
.MakeGenericMethod(propertyUnderlyingType);
return Expression.Call(null, containsMethod, arrayExpression, propertyExpression);
}
}
else // For other operators
{
// Handle null values for Equal and NotEqual operators
if (criteriaNode.Value == null)
{
if (criteriaNode.Operator == ComparisonOperator.Equal)
{
return Expression.Equal(propertyExpression, Expression.Constant(null, propertyType));
}
else if (criteriaNode.Operator == ComparisonOperator.NotEqual)
{
if (propertyType.IsValueType && Nullable.GetUnderlyingType(propertyType) != null)
{
// Property type is nullable
return Expression.Equal(propertyExpression, Expression.Constant(null, propertyType));
}
else if (propertyType.IsValueType)
{
// Property type is a non-nullable value type
// We can't directly compare it with null
// You may decide what behavior to implement here
// For example, throwing an exception or returning a constant false expression
throw new InvalidOperationException($"Cannot compare non-nullable value type {propertyType} with null.");
}
else
{
// Property type is a reference type
return Expression.NotEqual(propertyExpression, Expression.Constant(null, typeof(object)));
}
}
else
{
throw new NotSupportedException($"Comparison operator {criteriaNode.Operator} is not supported with null value.");
}
}
else // For non-null values
{
var constantValue = Convert.ChangeType(criteriaNode.Value, propertyType);
constant = Expression.Constant(constantValue);
}
// Build the appropriate comparison expression based on the operator
switch (criteriaNode.Operator)
{
case ComparisonOperator.Equal:
return Expression.Equal(propertyExpression, constant);
case ComparisonOperator.NotEqual:
return Expression.NotEqual(propertyExpression, constant);
case ComparisonOperator.Contains:
// Assuming the property is of type string, you can call the Contains method
return Expression.Call(propertyExpression, typeof(string).GetMethod("Contains", new[] { typeof(string) }), constant);
case ComparisonOperator.StartWith:
return Expression.Call(propertyExpression, typeof(string).GetMethod("StartsWith", new[] { typeof(string) }), constant);
case ComparisonOperator.GreaterThan:
return Expression.GreaterThan(propertyExpression, constant);
case ComparisonOperator.LessThan:
return Expression.LessThan(propertyExpression, constant);
case ComparisonOperator.GreaterThanOrEqual:
return Expression.GreaterThanOrEqual(propertyExpression, constant);
case ComparisonOperator.LessThanOrEqual:
return Expression.LessThanOrEqual(propertyExpression, constant);
default:
throw new NotSupportedException($"Comparison operator {criteriaNode.Operator} is not supported.");
}
}
}
private static Expression BuildGroupExpression<T>(FilterGroupNode groupNode, ParameterExpression parameter)
{
if (groupNode.Children == null || !groupNode.Children.Any())
throw new ArgumentException("Filter group must have child nodes.");
Expression combinedExpression = null;
foreach (var childFilter in groupNode.Children)
{
Expression childExpression;
if (childFilter is FilterCriteriaNode || childFilter is FilterGroupNode)
{
childExpression = BuildPredicate<T>(new List<FilterNode> { childFilter }, parameter).Body;
}
else
{
throw new ArgumentException($"Unknown filter node type: {childFilter.GetType().Name}");
}
combinedExpression = combinedExpression == null
? childExpression
: (groupNode.Operator == LogicalOperator.Or
? Expression.OrElse(combinedExpression, childExpression)
: Expression.AndAlso(combinedExpression, childExpression));
}
return combinedExpression;
}
When I am calling this method, it didn't generate a parameterized SQL query:
FAMSContext ctx = new FAMSContext();
var query = ctx
.ActiveAssets(null)
.ApplyFilter(new FilterCriteriaNode { FieldName = "Model.BrandId", Operator = ComparisonOperator.Equal, Value = "2618" })
.SelectBasicAssetModel();
string sql = query.ToQueryString();
This is the generated SQL:
SELECT [a].[AssetId], [a].[AssetCode], [a].[SerialNumber], [a].[LocationId], [m].[ModelName], [m].[Description] AS [ModelDescription], [b].[BrandName], [a0].[AssetTypeName], [c].[CategoryName]
FROM [Asset] AS [a]
INNER JOIN [Model] AS [m] ON [a].[ModelId] = [m].[ModelId]
INNER JOIN [Brand] AS [b] ON [m].[BrandId] = [b].[BrandId]
INNER JOIN [AssetType] AS [a0] ON [m].[AssetTypeId] = [a0].[AssetTypeId]
INNER JOIN [Category] AS [c] ON [m].[CategoryId] = [c].[CategoryId]
WHERE [m].[BrandId] = 2618
What should I do to make the EF Core could generate a parameterized SQL query from the returned IQueryable to avoid the SQL injection risk.
I tried many things to achieve this, but without success so far