Entity Framework 6 - How to determine stored procedure input parameters

What you're looking for is the equivelant of ADO.NET's SqlCommandBuilder.DeriveParameters() method. Unfortunately, to my knowledge, Entity Framework doesn't offer anything similar to this.

That said, assuming a Microsoft SQL Server database, you could query the database beforehand to get the list of parameters. This can be done using something similar to the following SQL:

SELECT      PARAMETER_NAME, 
            DATA_TYPE
FROM        information_schema.parameters
WHERE       specific_name = 'SellerModify'

I know this isn't exactly what you're looking for, but it may provide an alternative approach for solving your problem.

I was also looking for the similar solution but could not find anything until now. So I combined EF, SqlCommand, and SqlCommandBuilder.DeriveParameters(cmd).

/// <summary>
/// Prepare the SQL
/// </summary>
/// <param name="sqlText">sqlText contains StoreProcedure name</param>
/// <returns>Returns the prepared SQL</returns>
public (string sqlText, List<SqlParameter> parameters) PrepareSQL(string sqlText)
{
    List<SqlParameter> parameters = new List<SqlParameter>();
    using (var conn = new SqlConnection(db.Database.Connection.ConnectionString))
    {
        using (var cmd = new SqlCommand(sqlText, conn))
        {
            cmd.CommandType = CommandType.StoredProcedure;
            conn.Open();
            SqlCommandBuilder.DeriveParameters(cmd);

            foreach (SqlParameter item in cmd.Parameters)
            {
                if (item.Direction != ParameterDirection.ReturnValue)
                {
                    sqlText += item.ParameterName + ",";
                }

                if (item.Direction == ParameterDirection.Output || item.Direction == ParameterDirection.InputOutput)
                {
                    item.Direction = ParameterDirection.Output;
                    parameters.Add(item);
                }
            }
            sqlText = sqlText.Trim(',');
            cmd.Parameters.Clear();
        }
    }

    return (sqlText, parameters);
}

You can use item.Direction == ParameterDirection.Input for the input parameters in the if statement.

And you can consume it like this:

//Stored Procedure
string sqlText = "Report_Portfolio_Statement_Investor_Wise";
List<SqlParameter> parameters;
(sqlText, parameters) = PrepareSQL(sqlText);

//Input Parameters 
//I enter manually for now, could be automated later
parameters.AddRange(
    new List<SqlParameter>() 
    {
        new SqlParameter("@clientCode", clientCode),
        new SqlParameter("@reportDate", reportDate),
        new SqlParameter("@fromDate", fromDate)
    }
);

var data = db.Database.SqlQuery<PortfolioStatementInvestorReportVM>(sqlText, parameters.ToArray()).ToList();