Using In clause using ADO.net code

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SQL

ADO.NET

I am trying to use 'where in (a,b,c)' clause using ado.net and stored procedure. Below is the code.

SqlConnection sqlConnection1 = new SqlConnection("connectionstring");
                sqlConnection1.Open();

                var sqlCommand = new SqlCommand();
                sqlCommand.Connection = sqlConnection1;
                sqlCommand.CommandType = CommandType.StoredProcedure;


                var idList = new List<int> { 17, 55};
                var idParameterList = new List<string>();
                var index = 0;
                foreach (var id in idList)
                {
                    var paramName = "@idParam" + index;
                    sqlCommand.Parameters.AddWithValue(paramName, id);
                    idParameterList.Add(paramName);
                    index++;
                }


                sqlCommand.CommandText = String.Format("displayInfo",string.Join(",", idParameterList));    //displayinfo is Stored Procedeure Name

                using (SqlDataReader sqlReader = sqlCommand.ExecuteReader())
                {
                    var resultTable = new DataTable();
                    resultTable.Load(sqlReader);

                    // Do something with the result table
                }

                sqlConnection1.Close();

Stored Procedure

alter PROCEDURE displayInfo
@idParam varchar(max)
AS
BEGIN
    SELECT * FROM Table WHERE idParam IN (@idParam);
END
GO

And get below error-:

Procedure or function displayInfo has too many arguments specified.

Please Advise what should be the correct statement