Skip to content

Fix model binding for indexed IFormFile collections #67248

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
KieranDevvs wants to merge 3 commits into
base: main
Choose a base branch
from
+115 −2
Open

Fix model binding for indexed IFormFile collections #67248

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
3 commits
Select commit Hold shift + click to select a range
151429e
Added logic and tests to properly bind arrays to IFormFile collections.
KieranDevvs Jun 16, 2026
407aba2
Updated existing multi dimensional integration test to now expect fil…
KieranDevvs Jun 16, 2026
fa3cf54
Merge branch 'main' into bug/44398-form-file-binding-fix
KieranDevvs Jul 12, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
6 changes: 5 additions & 1 deletion src/Mvc/Mvc.Core/src/ModelBinding/Binders/FormFileModelBinder.cs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -150,7 +150,11 @@ private async Task GetFormFilesAsync(
continue;
}

if (file.Name.Equals(modelName, StringComparison.OrdinalIgnoreCase))
if (file.Name.Equals(modelName, StringComparison.OrdinalIgnoreCase) ||
(file.Name.Length >= modelName.Length + 2 &&

@gfoidl gfoidl Jun 18, 2026

Copy link
Copy Markdown
Member

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Suggested change
(file.Name.Length >= modelName.Length + 2 &&
(file.Name.Length - 2 >= modelName.Length &&

to prevent potential overflow.

@KieranDevvs KieranDevvs Jun 18, 2026

Copy link
Copy Markdown
Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Thanks for the suggestion.
I'm not currently seeing the problem the requested change solves.
Could you please share an example scenario where an overflow would occur?

file.Name.StartsWith(modelName, StringComparison.OrdinalIgnoreCase) &&
file.Name[modelName.Length] == '[' &&
file.Name[file.Name.Length - 1] == ']'))
{
postedFiles.Add(file);
}
Expand Down
90 changes: 90 additions & 0 deletions src/Mvc/Mvc.Core/test/ModelBinding/Binders/FormFileModelBinderTest.cs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -429,6 +429,96 @@ public async Task FormFileModelBinder_ReturnsFailedResult_ForCollectionsItCannot
Assert.Null(bindingContext.Result.Model);
}

[Fact]
public async Task FormFileModelBinder_ExpectMultipleFiles_WithIndexBinding_BindSuccessful()
{
// Arrange
var formFiles = new FormFileCollection
{
GetMockFormFile("file[0]", "file1.txt"),
GetMockFormFile("file[1]", "file2.txt"),
};
var httpContext = GetMockHttpContext(GetMockFormCollection(formFiles));
var bindingContext = GetBindingContext(typeof(IEnumerable<IFormFile>), httpContext);
var binder = new FormFileModelBinder(NullLoggerFactory.Instance);

// Act
await binder.BindModelAsync(bindingContext);

// Assert
Assert.True(bindingContext.Result.IsModelSet);

var entry = bindingContext.ValidationState[bindingContext.Result.Model];
Assert.False(entry.SuppressValidation);
Assert.Equal("file", entry.Key);
Assert.Null(entry.Metadata);

var files = Assert.IsAssignableFrom<IList<IFormFile>>(bindingContext.Result.Model);
Assert.Equal(2, files.Count);
Assert.Equal("file1.txt", files[0].FileName);
Assert.Equal("file2.txt", files[1].FileName);
}

[Fact]
public async Task FormFileModelBinder_ExpectMultipleFiles_WithNamedIndexBinding_BindSuccessful()
{
// Arrange
var formFiles = new FormFileCollection
{
GetMockFormFile("file[foo]", "file1.txt"),
GetMockFormFile("file[bar]", "file2.txt"),
};
var httpContext = GetMockHttpContext(GetMockFormCollection(formFiles));
var bindingContext = GetBindingContext(typeof(IEnumerable<IFormFile>), httpContext);
var binder = new FormFileModelBinder(NullLoggerFactory.Instance);

// Act
await binder.BindModelAsync(bindingContext);

// Assert
Assert.True(bindingContext.Result.IsModelSet);

var entry = bindingContext.ValidationState[bindingContext.Result.Model];
Assert.False(entry.SuppressValidation);
Assert.Equal("file", entry.Key);
Assert.Null(entry.Metadata);

var files = Assert.IsAssignableFrom<IList<IFormFile>>(bindingContext.Result.Model);
Assert.Equal(2, files.Count);
Assert.Equal("file1.txt", files[0].FileName);
Assert.Equal("file2.txt", files[1].FileName);
}

[Fact]
public async Task FormFileModelBinder_ExpectMultipleFiles_WithEmptyBracketBinding_BindSuccessful()
{
// Arrange
var formFiles = new FormFileCollection
{
GetMockFormFile("file[]", "file1.txt"),
GetMockFormFile("file[]", "file2.txt"),
};
var httpContext = GetMockHttpContext(GetMockFormCollection(formFiles));
var bindingContext = GetBindingContext(typeof(IEnumerable<IFormFile>), httpContext);
var binder = new FormFileModelBinder(NullLoggerFactory.Instance);

// Act
await binder.BindModelAsync(bindingContext);

// Assert
Assert.True(bindingContext.Result.IsModelSet);

var entry = bindingContext.ValidationState[bindingContext.Result.Model];
Assert.False(entry.SuppressValidation);
Assert.Equal("file", entry.Key);
Assert.Null(entry.Metadata);

var files = Assert.IsAssignableFrom<IList<IFormFile>>(bindingContext.Result.Model);
Assert.Equal(2, files.Count);
Assert.Equal("file1.txt", files[0].FileName);
Assert.Equal("file2.txt", files[1].FileName);
}

private static DefaultModelBindingContext GetBindingContextForReadOnlyArray(HttpContext httpContext)
{
var metadataProvider = new TestModelMetadataProvider();
Expand Down
21 changes: 20 additions & 1 deletion src/Mvc/test/Mvc.IntegrationTests/FormFileModelBindingIntegrationTest.cs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1116,7 +1116,26 @@ public async Task BindModelAsync_MultiDimensionalFormFile_WithArrayNotation()
Assert.True(modelBindingResult.IsModelSet);
var container = Assert.IsType<MultiDimensionalFormFileContainer>(modelBindingResult.Model);
Assert.NotNull(container.FormFiles);
Assert.Empty(container.FormFiles);
Assert.Equal(2, container.FormFiles.Length);

Assert.Single(container.FormFiles[0]);
Assert.Equal(2, container.FormFiles[1].Length);

Assert.Collection(
container.FormFiles,
item =>
{
Assert.Collection(
item,
file => Assert.Equal(data + 1, ReadFormFile(file)));
},
item =>
{
Assert.Collection(
item,
file => Assert.Equal(data + 2, ReadFormFile(file)),
file => Assert.Equal(data + 3, ReadFormFile(file)));
});
}

public class MultiDimensionalFormFileContainerLevel2
Expand Down
Loading