Input shape mismatch: Input 'dense_input' has shape 1,5, but input data is of length 1

Question

I'm trying to load an ONNX model in my C# project which I've trained using Python Keras. It gives me this error:

Unhandled Exception: System.InvalidOperationException: Input shape mismatch: Input 'dense_input' has shape 1,5, but input data is of length 1.

My program.cs file:

var context = new MLContext();
var data = context.Data.LoadFromEnumerable(new HeartInput[] { });
var inputColumns = new string[] { "dense_input" };
var outputColumns = new string[] { "dense_2" };
var pipeline = context.Transforms.ApplyOnnxModel(
                        outputColumnNames: outputColumns,
                        inputColumnNames: inputColumns,
                        modelFile: OnnxPath);
var model = pipeline.Fit(data);

HeartInput class:

public class HeartInput
{
    [ColumnName("dense_input")]
    public float DenseInput { get; set; }
}

When I check my ONNX model using Netron,

Is it because of the unk__ shape in my model? How to fix the error?