VectorType attribute with dynamic dimension while dealing with csv files

I am working on training and evaluation in ML.NET. The data comes from a .csv file. According to the requirements, there may be variable number of columns in the file. Until now, I have achieved this by providing a fixed vectorType dimension. But I am not aware of making this work dynamically.

Here is the a block of code working using the fixed dimension,

public class InputClass
{
public bool Lavel;

[VectorType(5)] // I want this to be dynamic
public string[] SpecVec;

public string PredictedTarget;
}

public static void Main(string[] args)
{
MLContext mlContext = new MLContext(seed:0);
TextLoader.Columns[] columns = new TextLoader.Columns[3];
columns[0] = new TextLoader.Column("Label", DataKind.Boolean, 0);
columns[2] = new TextLoader.Column("PredictedTarget", DataKind.String, 1);
columns[1] = new TextLoader.Column("SpecVec", DataKind.String, 2,6);

IDataView dataview = mlContext.Data.LoadFromTextFile(filepath, columns,
separatorChar:',', hasHeader:true, allowQuoting:false, trimWhitespace: true,
allowSparse:true);

//-- creating pipeline and training a model further

}
This code works without any issue. But I just need the VectorType to accept the dimension at runtime. Now it accepts only constant values. I am looking if there is any workaround to achieve this. I am a beginner into ML.Net, please do understand if I missed any steps or anything to be explained. I really appreciate any help to get this worked.