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GraphQl-Projector
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public class CategoryDao : IDisposable, IAsyncDisposable | |
{ | |
private readonly GraphContext context; | |
public CategoryDao(GraphContext context) | |
{ | |
this.context = context; | |
} | |
public async Task<Category> FindByIdAsync(int categoryId, IEnumerable<string> requiredFields = null) | |
{ | |
var query = this.context.Categories.AsNoTracking(); | |
if (StaticSettings.ProjectionEnabled && (requiredFields?.Any() ?? false)) | |
{ | |
var projection = ProjectionBuilder | |
.Get<Category>() | |
.WithProperties(requiredFields.Append(nameof(Category.CategoryID))) | |
.ExcludeProperties(this.context?.IgnoredMembers?.GetIgnoredMembers<Category>()) | |
.Build(); | |
query = query.Select(projection); | |
} | |
return await query.FirstOrDefaultAsync(x => x.CategoryID == categoryId); | |
} | |
} |
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public class IgnoredMembersCollection | |
{ | |
private readonly ModelBuilder builder; | |
private Dictionary<Type, IReadOnlyList<string>> ignoredLists; | |
public IgnoredMembersCollection(ModelBuilder builder) | |
{ | |
this.builder = builder; | |
this.ignoredLists = new Dictionary<Type, IReadOnlyList<string>>(); | |
} | |
public IReadOnlyList<string> GetIgnoredMembers<TEntity>() where TEntity : class | |
{ | |
if (!this.ignoredLists.TryGetValue(typeof(TEntity), out var metadata)) | |
{ | |
this.ignoredLists[typeof(TEntity)] = metadata = this.builder.Entity<TEntity>().Metadata.GetIgnoredMembers(); | |
} | |
return metadata; | |
} | |
} | |
public class GraphContext : DbContext, IDisposable | |
{ | |
private static IgnoredMembersCollection ignoredMembers { get; set; } | |
public IgnoredMembersCollection IgnoredMembers | |
{ | |
get | |
{ | |
if (ignoredMembers == null) | |
{ | |
//Forcing initialisation | |
base.Model.GetEntityTypes(); | |
} | |
if (ignoredMembers == null) | |
{ | |
Debugger.Break(); | |
} | |
return ignoredMembers; | |
} | |
} | |
public DbSet<Category> Categories { get; set; } | |
public GraphContext(DbContextOptions options) | |
: base(options) | |
{ | |
} | |
protected override void OnModelCreating(ModelBuilder builder) | |
{ | |
ignoredMembers = new IgnoredMembersCollection(builder); | |
} | |
} | |
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public static class GraphQLExtensions { | |
public static IEnumerable<string> GetRequiredFieldNames<TSource>(this ResolveFieldContext<TSource> source, bool includeSubSelections = false) | |
{ | |
var fieldTypes = GetFieldTypes(source.ReturnType); | |
var query = source.FieldAst.SelectionSet.Selections | |
.OfType<Field>() | |
.Where(x => !x.Arguments.Any()); | |
if (!includeSubSelections) | |
{ | |
query = query.Where(x => x.SelectionSet.Selections.Count == 0); | |
} | |
return SelectOriginalName(query); | |
IEnumerable<FieldType> GetFieldTypes(IGraphType returnType) | |
{ | |
if (returnType is IComplexGraphType cgt) | |
{ | |
return cgt.Fields; | |
} | |
if (returnType is ListGraphType lgt) | |
{ | |
return GetFieldTypes(lgt.ResolvedType); | |
} | |
throw new NotImplementedException($"Cannot resolve returntype of '{returnType.GetType().FullName}'"); | |
} | |
IEnumerable<string> SelectOriginalName(IEnumerable<Field> input) | |
{ | |
foreach (var field in input) | |
{ | |
var fieldType = fieldTypes.FirstOrDefault(x => string.Equals(x.Name, field.Name, StringComparison.OrdinalIgnoreCase)); | |
if (fieldType == null) | |
{ | |
yield return field.Name; | |
continue; | |
} | |
if (fieldType.Metadata.TryGetValue(SharedConstants.OriginalPropertyName, out var originalName)) | |
{ | |
yield return originalName.ToString(); | |
continue; | |
} | |
yield return field.Name; | |
} | |
} | |
} | |
} |
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public class GraphQuery { | |
public GraphQuery(IMapper mapper) | |
{ | |
this.FieldAsync<CategoryType>( | |
"category", | |
arguments: new QueryArguments( | |
new QueryArgument<NonNullGraphType<IntGraphType>> { Name = "id", Description = "id of the category" } | |
), | |
resolve: async context => | |
{ | |
var categoryId = context.GetArgument<int>("id"); | |
var requiredFields = context.GetRequiredFieldNames(); | |
var cat = await context.Get<CategoryDao>().FindByIdAsync(categoryId, requiredFields); | |
return cat; | |
}); | |
} | |
} |
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public class ProjectionBuilder | |
{ | |
public static ProjectionBuilder<T> Get<T>() | |
{ | |
return new ProjectionBuilder<T>(); | |
} | |
} | |
public class ProjectionBuilder<T> | |
{ | |
private IEnumerable<string> properties; | |
private IEnumerable<string> excludedProperties; | |
public ProjectionBuilder() | |
{ | |
this.properties = Enumerable.Empty<string>(); | |
this.excludedProperties = Enumerable.Empty<string>(); | |
} | |
public ProjectionBuilder<T> WithProperties(IEnumerable<string> properties) | |
{ | |
if (properties == null) | |
{ | |
return this; | |
} | |
this.properties = this.properties.Concat(properties); | |
return this; | |
} | |
public ProjectionBuilder<T> ExcludeProperties(IEnumerable<string> properties) | |
{ | |
if (properties == null) | |
{ | |
return this; | |
} | |
this.excludedProperties = this.excludedProperties.Concat(properties); | |
return this; | |
} | |
public Expression<Func<T, T>> Build() | |
{ | |
var requiredProperties = properties.Except(this.excludedProperties, StringComparer.InvariantCultureIgnoreCase) | |
.Select(x => typeof(T).GetProperty(x, comparisonType: StringComparison.InvariantCultureIgnoreCase)) | |
.Where(x => x != null); | |
return this.Build(requiredProperties); | |
} | |
private Expression<Func<T, T>> Build(IEnumerable<PropertyInfo> requiredProperties) | |
{ | |
var parameterExpression = Expression.Parameter(typeof(T), "x"); | |
var memberBindings = requiredProperties.Select(x => Expression.Bind(x, Expression.Property(parameterExpression, x))); | |
return Expression.Lambda<Func<T, T>>(Expression.MemberInit(Expression.New(typeof(T)), memberBindings), new ParameterExpression[] { parameterExpression }); | |
} | |
} |
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