Description

When creating a Modal TextInput with the style Short and setting the value to a multi-line string, the error received will say just "Invalid Form Body", without exact feedback to the developer what the issue is.

// var description = <multi-line string>

var builder = new ModalBuilder()
{
    Title = "Custom modal",
    CustomId = "custom-id"
};

builder.AddTextInput("Description", "description", placeholder: "Description", value: description, required: true);

var modal = builder.Build();

// send modal

This will cause an error:

The server responded with error 50035: Invalid Form Body
COMPONENT_VALIDATION_FAILED: Component validation failed

Changes

In TextInputBuilder we check if the value set is a multi-line string by checking the presence of \n and if the Style is short we throw a ArgumentException.

Currently it would still be possible to cause this error by doing the following step:

1. Set Style to Paragraph
2. Set multi-line string
3. Change Style to Short

Additional checks could be set if requested to the setter of TextInputStyle property