How to validate CSV file whether it is in correct format or not ?

Hi Sachin,
You can add the following code in validations parameter of a!fileUploadfield() that will check where the file is in .csv format 
code:

validations: {
a!localVariables(
local!invalidExtensions: difference(
upper(fv!files.extension),
{ "CSV"}
),

if(
length(local!invalidExtensions) > 0,
"Please upload supported file formats: CSV",
""
)
)
}

Hello sachink2402 

What do you mean format? Do you mean the file extension type? If so below the code that would help.

{
  a!fileUploadField(
    label: "File Upload",
    labelPosition: "ABOVE",
    target: cons!FOLDER_CONSTANT,
    saveInto: ri!file,
    value: ri!file,
    validations: a!localVariables(
      local!invalidExtensions: difference(upper(fv!files.extension), "CSV"),
      if(
        length(local!invalidExtensions) > 0,
        "Attachments must be pdf files. Remove: " & index(
          fv!files,
          "name",
          wherecontains(
            local!invalidExtensions,
            upper(fv!files.extension)
          ),
          {}
        ),
        ""
      )
    )
  )
}

Validation from documentation. Please refer THIS for more information

docs.appian.com/.../File_Upload_Component.html

Typically when uploading an processing a CSV file (unless it is very small) we use an asynchronous pattern. The file is uploaded and the contents loaded to a staging table. The contents can then be validated and then, if valid, the data moved to the target operational table(s).

In terms of implementing the actual validation, you can use JSON Schema Validation for the vast majority of the typical validations that you might want to apply.

Use the JSON Tools plug-in the conduct JSON Schema validation (obviously you'll need convert your data in your staging table to JSON). If the volumes are very large you'll probably want to throttle the processing so as to not consume too much server resource in one go. If there are any Schema violations you'll need to write these somewhere. Whether the validation passes or fails you'll need to inform the original user since the processing is conducted asynchronously form the initial file upload.

Visit JSON Schema Org for help with JSON Schemas