用返回值调用存储过程

您需要在命令中添加return参数：

using (SqlConnection conn = new SqlConnection(getConnectionString()))using (SqlCommand cmd = conn.CreateCommand()){    cmd.CommandText = parameterStatement.getQuery();    cmd.CommandType = CommandType.StoredProcedure;    cmd.Parameters.AddWithValue("SeqName", "SeqNamevalue");    var returnParameter = cmd.Parameters.Add("@ReturnVal", SqlDbType.Int);    returnParameter.Direction = ParameterDirection.ReturnValue;    conn.Open();    cmd.ExecuteNonQuery();    var result = returnParameter.Value;}