1. Framework Structure: .NET Core is a cross-platform, open-source framework developed by Microsoft, while Spring is a Java-based framework commonly used for enterprise applications. .NET Core offers a modular architecture where only required components can be included, whereas Spring provides a more opinionated structure with various modules tightly integrated within the framework.

2. Programming Language: .NET Core primarily supports C# as the programming language, while Spring supports Java. C# provides features like properties, LINQ, and async programming, whereas Java is known for its portability, scalability, and strong community support.

3. IDE Support: .NET Core is well-integrated with Microsoft Visual Studio, providing a cohesive development environment with tools like IntelliSense and debugging capabilities. Spring, on the other hand, has good support for popular IDEs like Eclipse and IntelliJ IDEA, along with community plugins to enhance development experience.

4. Dependency Injection: Dependency injection is a first-class citizen in both .NET Core and Spring, but with different implementations. .NET Core uses a built-in IOC container for dependency injection, providing a more native and straightforward approach. Spring, on the other hand, relies on frameworks like Spring Framework and Spring Boot for dependency injection management.

5. Deployment Options: .NET Core applications can be deployed as stand-alone executables, self-contained deployments, or Docker containers, offering flexibility in deployment options. Spring applications are typically deployed on Java Virtual Machine (JVM), making them compatible with various cloud platforms like AWS, Azure, and Google Cloud.

In Summary, the key differences between .NET Core and Spring lie in their framework structure, programming language support, IDE integration, dependency injection mechanisms, and deployment options.