When to choose Agile and when to choose traditional SDLC for software project?

Thank you for invitation. But I did not work in software project 

Can you chose or even can you switch? These methodologies depends heavily on team skills, team training, and tools. It will be difficult to make you team work on a methodology for a project then switch them on another one for the next project. 

The methodology needs to be decided based on the project type and the organizational environment.

Traditional SDLC best suits when you have solid requirements and know what the end results are.

Agile would suit when there are uncertainty and unambigious requirements.  You would want to involve business closely and deliver incrementally and iteratively.

According to the project type and the best practice that we have

SDLC - should be used for a long time project development.

Agile - should be used for a short time project development (most likely, applications that are already implemented or need an enhancements.)

If a project can be developed and released in pieces then agile

else, a project which has to be delivered at one go as a full product then SDLC, where scope and requirements are locked initially.

1. Agile management iterative and incremental method of managing the project. Now a day90% projects are developing in this process. Flexible to accept the changes at any time. 
2. Traditional SDLC (Water fall method): This is sequentially process and not acceptable any changes during the development process. 

Agile practice - is for the new requirements and enhancements to the already existing systems.

Traditional SDLC is for a new system to be building as a whole.

Agile shall be followed for both unambiguous requirement and ambiguous requirement  type. Agile give option to review the product result periodically before releasing it. Changes can be done if and when required. Number of features rejection from end customer will be less.