String Comparisons

AutoFilterer provides a strong API to define string comparisons in the DTOs. StringFilterOptions attribute is used to define a comparison. The attribute is optional. Default value is Equals.

Options

There are 4 options available for string comparisons:

• Equals: Generates a filter that checks if the value is equal to the specified value.

    [StringFilterOptions(StringComparison.Equals)]
    public string Name { get; set; }
  

  Generated LINQ expression: x => Name == "John"

• StartsWith: Generates a filter that checks if the value starts with the specified value.

  [StringFilterOptions(StringComparison.StartsWith)]
  public string Name { get; set; }
  

  Generated LINQ expression: x => Name.StartsWith("John")

• EndsWith: Generates a filter that checks if the value ends with the specified value.

  [StringFilterOptions(StringComparison.EndsWith)]
  public string Name { get; set; }
  

  Generated LINQ expression: x => Name.EndsWith("John")

• Contains: Generates a filter that checks if the value contains the specified value.

  [StringFilterOptions(StringComparison.Contains)]
  public string Name { get; set; }
  

  Generated LINQ expression: x => Name.Contains("John")

Comparisons

System.StringComparison is used to define the comparison type as a second parameter. It can be used to filter case-insensitive queries.

[StringFilterOptions(StringFilterOption.Contains, StringComparison.InvariantCultureIgnoreCase)]
public string Name { get; set; }

Generated LINQ expression: x => Name.Contains("John", StringComparison.InvariantCultureIgnoreCase)

Common Issues

Database providers don't support same logic while generating database queries from LINQ expressions. StringComparison.InvariantCultureIgnoreCase is not supported by all database providers. As a workaround, you can use ToLower() method and database provider accepts it's a case insensitive query. MongoDB and SqlServer uses that logic to generate case-insensitive queries.

Achieving ToLower() expression generation, you need to use ToLowerContainsComparison attribute. It'll generate a a proper x => x.Name.ToLower().Contains("John") expression.

    [ToLowerContainsComparison]
    public string Name { get; set; }